diff --git a/CONNECTOR.md b/CONNECTOR.md
index f91196f..03b98b8 100644
--- a/CONNECTOR.md
+++ b/CONNECTOR.md
@@ -1,10 +1,10 @@
 # Connector
 
-This file documents the Connection and Version Negotiation logic.
+This file documents the connection and version negotiation logic.
 
 ## Registry
 
-The `registry` crate provides a multi-version `Registry` used by the host for version negotiation. Accessed through the `mtp` facade (requires the `host` feature):
+The `registry` module provides a multi-version `Registry` used by the host for version negotiation. Accessed through the `mtp` facade (requires the `host` feature):
 
 ```rust
 use mtp::codec::registry::Registry;
@@ -33,11 +33,12 @@ The host creates a QUIC server, manages the registry, and handles version negoti
 
 ### Initialization
 
+The host binds to the address from the `mtp_BIND` environment variable (defaults to `::`) on the specified port:
+
 ```rust
 use mtp::host::{MTPHost, HostConfig};
 
 let config = HostConfig {
-    ip: "::".into(),
     port: 4433,
     tls_fullchain: std::fs::read("cert.pem")?,
     tls_key: std::fs::read("key.pem")?,
@@ -50,35 +51,31 @@ let mut host = MTPHost::new(config).await?;
 
 ```rust
 while let Some(conn) = host.accept().await {
-    /*
-     *  conn.version is the negotiated version
-     * conn.codec is a VersionedCodec scoped to that version
-     * conn.sender / conn.receiver for raw CommunicationValue I/O
-     */
+    // conn.version is the negotiated version
+    // conn.codec is a VersionedCodec scoped to that version
+    // conn.sender / conn.receiver for raw CommunicationValue I/O
 
     let msg = conn.receiver.receive().await?;
-    // ...
 }
 ```
 
 The host's `accept()` method:
 1. Accepts a QUIC connection
-2. Reads the first `CommunicationValue` (always encoded with reserved type IDs)
-3. Extracts the client's protocol version from `DataType::Version` (wire ID 3)
-4. Calls `registry.negotiate(&[client_version])`
-5. Returns `None` if the version is unsupported (caller sends `ErrorBadVersion` and disconnects)
-6. Returns an `MTPConnection` with the negotiated version otherwise
+2. If authentication is required (crypto feature): performs login/register handshake
+3. Reads the first `CommunicationValue` (always encoded with reserved type IDs)
+4. Extracts the client's protocol version from `DataType::Version` (wire ID 3)
+5. Calls `registry.negotiate(&[client_version])`
+6. Returns `None` if the version is unsupported
+7. Returns an `MTPConnection` with the negotiated version otherwise
 
-### Login/Register Flow
+### Login/Register Handshake (crypto feature)
 
-The complete login/register handshake (see design docs) builds on top of `MTPConnection`:
+When `require_authentication` is set, the host sends a **greeting** first (host ID, public keys, nonce). The client then responds with either:
 
-1. Client sends `Identification` with version, ID, nonce, signature
-2. Host verifies signature via `get_key` callback
-3. Host responds with approval + nonces + signature
-4. Client verifies response
+- **Login** (`CommunicationType::Identification`, ID 15): client ID, nonce, signature
+- **Register** (`CommunicationType::Register`, ID 17): public keys, nonce, signature
 
-New clients use the `Register` variant instead, presenting their public key for registration.
+The host verifies the client's signature, sends a signed response, and the client verifies the host's signature.
 
 ---
 
@@ -94,13 +91,14 @@ let config = ClientConfig {
     server_cert: None, // or Some(cert_pem_bytes)
 };
 
-// Connect (existing client)
+// Connect (unauthenticated, existing client)
 let conn = MTPClient::connect(config, 8765).await?;
 
-/*
- *  conn.version is the compiled-in PROTOCOL_VERSION
- *  conn.sender / conn.receiver for I/O
- */
+// Authenticated login
+let conn = MTPClient::auth_connect(config, 8765, keys, host_pk).await?;
+
+// Registration (new client)
+let conn = MTPClient::auth_register(config, keys, host_pk).await?;
 ```
 
 The client's `PROTOCOL_VERSION` constant is set by `protocol_version` in `type-maps.yaml` and baked in at compile time. The client never imports the `registry` crate; it only uses `mtp::type_map` for enum types and `mtp::codec` for encoding.
@@ -111,26 +109,26 @@ The client's `PROTOCOL_VERSION` constant is set by `protocol_version` in `type-m
 
 ```
 Client (v2.0)         Host (v0.0, v1.0, v2.0)
-    │                        │
-    │  QUIC connect          │
-    │───────────────────────→│
-    │                        │
-    │  CommValue{ Ident. }   │
-    │    Version → "2.0"     │
-    │    Id → 8765           │
-    │    Nonce → ...         │
-    │    Signature → ...     │
-    │───────────────────────→│
-    │                        │  registry.negotiate(&[Version(2,0)])
-    │                        │  → Some(Version(2,0))
-    │                        │
-    │  Response              │
-    │←───────────────────────│  (uses v2.0 TypeMap for encoding)
-    │    Status, Nonces,     │
-    │    Signature           │
-    │                        │
-    │  (subsequent messages  │
-    │   use v2.0 TypeMap)    │
+    |                        |
+    |  QUIC connect          |
+    |----------------------->|
+    |                        |
+    |  CommValue{ Ident. }   |
+    |    Version -> "2.0"    |
+    |    Id -> 8765          |
+    |    Nonce -> ...        |
+    |    Signature -> ...    |
+    |----------------------->|
+    |                        |  registry.negotiate(&[Version(2,0)])
+    |                        |  -> Some(Version(2,0))
+    |                        |
+    |  Response              |
+    |<-----------------------|  (uses v2.0 TypeMap for encoding)
+    |    Status, Nonces,     |
+    |    Signature           |
+    |                        |
+    |  (subsequent messages  |
+    |   use v2.0 TypeMap)    |
 ```
 
-If the client sends an unsupported version (e.g. v3.0 when the host only knows up to v2.0), `negotiate` returns `None` and the host sends `ErrorBadVersion` using reserved types.
+If the client sends an unsupported version (e.g. v3.0 when the host only knows up to v2.0), `negotiate` returns `None` and the connection is closed.
diff --git a/Cargo.toml b/Cargo.toml
index 2627783..b09bee7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,13 +33,19 @@ mtp-codec = { path = "codec" }
 mtp-transport = { path = "transport" }
 
 # --- optional, behind features ---
-mtp-crypto = { path = "crypto", optional = true }
+mtp-crypto = { path = "crypto", optional = true, features = [
+    "serde",
+    "mlkem-tls",
+] }
 mtp-host = { path = "host", optional = true }
 mtp-client = { path = "client", optional = true }
 
 [features]
 default = []
 
+# Serialization
+serde = ["mtp-crypto/serde"]
+
 # Message encryption (AEAD, signatures, KEM, KDF, hashing).
 # When combined with `host` or `client`, also enables connection authentication.
 crypto = [
diff --git a/README.md b/README.md
index 57e2412..3c4b139 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
-# **M**ethanium **T**ransport **P**rotocol
+# Methanium Transport Protocol
 
-**MTP** is a **m**odular **t**ransport **p**rotocol by Methanium.
+MTP is a modular transport protocol built on QUIC. It provides version-negotiable type maps, a binary codec, cryptographic primitives (classical and post-quantum), and host/client connection management with mutual authentication.
 
 ## Getting Started
 
@@ -22,9 +22,9 @@ The `mtp` umbrella crate re-exports all sub-crates behind feature flags:
 Core crates (`codec`, `transport`, `common`, `type_map`) are always available.
 
 ```rust
-use mtp::codec::{encode, decode, DataValue};
-use mtp::type_map::TypeMap;
-use mtp::transport::Sender;
+use mtp::codec::{CommunicationValue, DataValue};
+use mtp::type_map::{CommunicationType, DataType, TypeMap};
+use mtp::transport::{Sender, Receiver};
 
 #[cfg(feature = "crypto")]
 use mtp::crypto::ChaCha20Poly1305;
@@ -32,38 +32,47 @@ use mtp::crypto::ChaCha20Poly1305;
 
 ## Sub-crates
 
-All sub-crates are re-exported through the `mtp` facade and can be referenced
-as `mtp::codec`, `mtp::transport`, `mtp::common`, `mtp::type_map`,
-`mtp::crypto`, `mtp::host`, `mtp::client`.
+All sub-crates are re-exported through the `mtp` facade and can be referenced as `mtp::codec`, `mtp::transport`, `mtp::common`, `mtp::type_map`, `mtp::crypto`, `mtp::host`, `mtp::client`.
 
 ### Codec
 
-The Codec crate handles encoding and decoding of MTP packets using Communication Types and Data Types from the Registry.
+The codec crate handles binary encoding and decoding of MTP packets using Communication Types and Data Types resolved through the type-map registry.
 
-**Data Values:**
-- Container
-- Encrypted Container (requires `crypto` feature)
-- Signed Integer
-- Unsigned Integer
+**Data Value types:**
+- Container (key-value map of typed entries)
+- Encrypted Container (requires `crypto`)
+- Signed Container (requires `crypto`)
+- SignedEncrypted Container (requires `crypto`)
+- Signed Integer (i128)
+- Unsigned Integer (u128)
 - Boolean
-- Signed Float
+- Float (exponent + mantissa)
 - String
 - Array
-- Binary (List of Bytes)
+- Bytes
+- Null
 
-Encoding/decoding uses a `TypeMap` to resolve type names to wire IDs.
-
-The Codec uses the Crypto crate to encrypt and decrypt Encrypted Containers.
-
----
+Encoding and decoding use a `TypeMap` to resolve type names to wire IDs. The `CommunicationValue` struct provides the frame format (type, flags, optional id/sender/receiver, data payload, optional signature).
 
 ### Transport
 
-The Transport crate wraps QUIC using `wtransport`. It provides `Sender`/`Receiver` for bidirectional message passing over QUIC streams.
+The transport crate wraps QUIC using `wtransport`. It provides `Sender`/`Receiver` for bidirectional message passing over uni-directional QUIC streams. Supports two send modes: persistent stream and single-stream-per-message.
+
+### Host
+
+The host crate provides `MTPHost` with built-in version negotiation and optional authenticated login/registration (requires `crypto`). Accepts connections, negotiates protocol version, and returns `MTPConnection` handles.
+
+### Client
+
+The client crate provides `MTPClient` that connects to an MTP host. Supports `connect` (unauthenticated), `auth_connect` (login), and `auth_register` (registration) when built with `crypto`.
 
 ### Common
 
-Common handles logging and error handling. Personal information reported to Common will be anonymized.
+Common defines shared error types (`CodecError`, `CommunicationError`) used across all crates.
+
+### Type Map
+
+The type-map build script reads a YAML configuration to generate `CommunicationType` and `DataType` enums at compile time. The runtime crate provides `TypeMap`, `Version`, `CommunicationTypeId`, `DataTypeId`, and the multi-version `Registry` (requires `registry` feature).
 
 ### Crypto Stack
 
@@ -77,3 +86,16 @@ Common handles logging and error handling. Personal information reported to Comm
 | sha2             | No       | Standard construction; widely reviewed           |
 | zeroize          | No       | Simple; widely used                              |
 | mlkem-tls        | No       | mlkem-rs backend unaudited                       |
+
+## Test Coverage
+
+| Crate          | Tests | Notes                                      |
+| -------------- | ----- | ------------------------------------------ |
+| common         | 7     | Error type Display, Clone, format          |
+| type-map       | 3     | Registry builtin, negotiate, latest        |
+| codec          | 32    | DataValue roundtrip, accessors, Display, Hash, base64; CommunicationValue frame encode/decode |
+| crypto         | 20    | AEAD, signatures, KEM, KDF, hash, key types, multi-encrypt |
+| transport      | 12    | ConnectionHandle state transitions; Policy defaults; SendMode |
+| host           | 3     | Version extraction from messages           |
+| client         | 7     | ClientConfig; AuthState derives            |
+| **Total**      | **84** |                                            |
diff --git a/client/src/lib.rs b/client/src/lib.rs
index 4d030d2..0df6e7e 100644
--- a/client/src/lib.rs
+++ b/client/src/lib.rs
@@ -7,6 +7,7 @@ use mtp_transport::{Policy, Receiver, Sender};
 pub struct ClientConfig {
     pub url: String,
     pub server_cert: Option<Vec<u8>>,
+    pub client_id: u64,
 }
 
 // Established MTP connection with a single negotiated version.
@@ -37,10 +38,7 @@ impl MTPClient {
      * The first message includes the client's protocol version
      * (a reserved `Version` data entry) so the host can negotiate.
      */
-    pub async fn connect(
-        config: ClientConfig,
-        client_id: u64,
-    ) -> Result<MTPConnection, CommunicationError> {
+    pub async fn connect(config: ClientConfig) -> Result<MTPConnection, CommunicationError> {
         let (sender, receiver) =
             mtp_transport::connect(&config.url, config.server_cert, Policy::default()).await?;
 
@@ -48,7 +46,10 @@ impl MTPClient {
         let version_str = format!("{}", PROTOCOL_VERSION);
         let ident = CommunicationValue::new(mtp_codec::CommunicationType::Identification)
             .add_data(DataTypeId(3), DataValue::Str(version_str))
-            .add_data(DataTypeId(6), DataValue::UnsignedNumber(client_id.into()));
+            .add_data(
+                DataTypeId(6),
+                DataValue::UnsignedNumber(config.client_id.into()),
+            );
 
         sender.send(&ident).await?;
 
@@ -59,7 +60,7 @@ impl MTPClient {
             #[cfg(feature = "crypto")]
             auth_state: AuthState::Authenticated,
             #[cfg(feature = "crypto")]
-            client_id,
+            client_id: config.client_id,
         })
     }
 }
@@ -69,50 +70,58 @@ impl MTPClient {
 impl MTPClient {
     pub async fn auth_connect(
         config: ClientConfig,
-        client_id: u64,
-        keys: mtp_crypto::KeyGroup,
-        host_public_key: mtp_crypto::SignaturePublicKey,
+        keys: &mtp_crypto::Keyring,
+        host_public_key_bundle: &mtp_crypto::PublicKeyBundle,
     ) -> Result<MTPConnection, CommunicationError> {
-        use mtp_crypto::{Ed25519Signer, SignatureScheme, verify_ed25519};
+        use mtp_crypto::{
+            Ed25519Signer, MlDsaSigner, SignatureScheme, verify_ed25519, verify_ml_dsa,
+        };
 
         let (sender, receiver) =
             mtp_transport::connect(&config.url, config.server_cert, Policy::default()).await?;
 
-        // 1. Receive host greeting (IdentificationResponse with host ID, public keys, nonce)
-        let _greeting = receiver.receive().await?;
-
-        // 2. Build and send Identification message with auth data
+        // 1. Build and send Identification message immediately (no greeting)
         let client_nonce: u128 = rand::random();
         let version_str = format!("{}", PROTOCOL_VERSION);
 
         let mut sig_payload = Vec::new();
         sig_payload.extend_from_slice(version_str.as_bytes());
-        sig_payload.extend_from_slice(&client_id.to_be_bytes());
+        sig_payload.extend_from_slice(&config.client_id.to_be_bytes());
         sig_payload.extend_from_slice(&client_nonce.to_be_bytes());
 
-        let signer = Ed25519Signer::new(&keys.signature_private_key)
+        let signer = Ed25519Signer::new(&keys.sig_cl_secret_key)
             .map_err(|e| CommunicationError::Other(e.to_string()))?;
 
         /* ===== Signature ===== */
-        // Current: signing concatenated bytes
-        // Future: sign entire CommunicationValue
         let signature = signer
             .sign(&sig_payload)
             .map_err(|e| CommunicationError::Other(e.to_string()))?;
-        /* ===== End Signature ===== */
 
-        let ident = CommunicationValue::new(mtp_codec::CommunicationType::Identification)
+        let mut ident = CommunicationValue::new(mtp_codec::CommunicationType::Identification)
             .add_typed_default(DataType::Version, DataValue::Str(version_str))
-            .add_typed_default(DataType::Id, DataValue::UnsignedNumber(client_id as u128))
+            .add_typed_default(
+                DataType::Id,
+                DataValue::UnsignedNumber(config.client_id as u128),
+            )
             .add_typed_default(
                 DataType::ClientNonce,
                 DataValue::UnsignedNumber(client_nonce),
             )
             .add_typed_default(DataType::Signature, DataValue::Bytes(signature));
 
+        if !keys.sig_pq_secret_key.as_bytes().is_empty() {
+            let pq_signer = MlDsaSigner::new(&keys.sig_pq_secret_key, &keys.sig_pq_public_key)
+                .map_err(|e| CommunicationError::Other(e.to_string()))?;
+            let pq_signature = pq_signer
+                .sign(&sig_payload)
+                .map_err(|e| CommunicationError::Other(e.to_string()))?;
+            ident = ident.add_typed_default(DataType::PqSignature, DataValue::Bytes(pq_signature));
+        }
+        /* ===== End Signature ===== */
+
         sender.send(&ident).await?;
 
-        // 3. Receive host response
+        // 2. Receive host response (single message)
         let response = receiver.receive().await?;
 
         let connected = response.get_data(DataTypeId(11));
@@ -158,15 +167,36 @@ impl MTPClient {
             }
         };
 
+        let host_pq_sig = match response.get_data(DataTypeId(12)) {
+            DataValue::Bytes(b) => b.clone(),
+            _ => vec![],
+        };
+
         let mut host_sig_payload = Vec::new();
-        host_sig_payload.extend_from_slice(b"true");
+        host_sig_payload.push(0x01);
+        host_sig_payload.extend_from_slice(&config.client_id.to_be_bytes());
         host_sig_payload.extend_from_slice(&client_nonce.to_be_bytes());
         host_sig_payload.extend_from_slice(&host_new_nonce.to_be_bytes());
 
         /* ===== Signature ===== */
-        verify_ed25519(&host_public_key, &host_sig_payload, &host_sig).map_err(|_| {
-            CommunicationError::AuthenticationFailed("Host signature invalid".into())
-        })?;
+        verify_ed25519(
+            &host_public_key_bundle.sig_cl_public_key,
+            &host_sig_payload,
+            &host_sig,
+        )
+        .map_err(|_| CommunicationError::AuthenticationFailed("Host signature invalid".into()))?;
+        if !host_pq_sig.is_empty()
+            && verify_ml_dsa(
+                &host_public_key_bundle.sig_pq_public_key,
+                &host_sig_payload,
+                &host_pq_sig,
+            )
+            .is_err()
+        {
+            return Err(CommunicationError::AuthenticationFailed(
+                "Host PQ signature invalid".into(),
+            ));
+        }
         /* ===== End Signature ===== */
 
         Ok(MTPConnection {
@@ -174,24 +204,23 @@ impl MTPClient {
             sender,
             receiver,
             auth_state: AuthState::Authenticated,
-            client_id,
+            client_id: config.client_id,
         })
     }
 
     pub async fn auth_register(
         config: ClientConfig,
-        keys: mtp_crypto::Keyring,
-        host_public_key: mtp_crypto::SignaturePublicKey,
+        keys: &mtp_crypto::Keyring,
+        host_public_key_bundle: &mtp_crypto::PublicKeyBundle,
     ) -> Result<MTPConnection, CommunicationError> {
-        use mtp_crypto::{Ed25519Signer, SignatureScheme, verify_ed25519};
+        use mtp_crypto::{
+            Ed25519Signer, MlDsaSigner, SignatureScheme, verify_ed25519, verify_ml_dsa,
+        };
 
         let (sender, receiver) =
             mtp_transport::connect(&config.url, config.server_cert, Policy::default()).await?;
 
-        // 1. Receive host greeting (IdentificationResponse with host ID, public keys, nonce)
-        let _greeting = receiver.receive().await?;
-
-        // 2. Build and send Register message with public keys and auth data
+        // 1. Build and send Register message immediately
         let client_nonce: u128 = rand::random();
         let version_str = format!("{}", PROTOCOL_VERSION);
         let pk_bundle = keys.public_key_bundle();
@@ -209,9 +238,8 @@ impl MTPClient {
         let signature = signer
             .sign(&sig_payload)
             .map_err(|e| CommunicationError::Other(e.to_string()))?;
-        /* ===== End Signature ===== */
 
-        let register = CommunicationValue::new(mtp_codec::CommunicationType::Register)
+        let mut register = CommunicationValue::new(mtp_codec::CommunicationType::Register)
             .add_typed_default(DataType::Version, DataValue::Str(version_str))
             .add_typed_default(
                 DataType::ClientNonce,
@@ -220,9 +248,20 @@ impl MTPClient {
             .add_typed_default(DataType::PublicKeys, DataValue::Bytes(pk_bytes))
             .add_typed_default(DataType::Signature, DataValue::Bytes(signature));
 
+        if !keys.sig_pq_secret_key.as_bytes().is_empty() {
+            let pq_signer = MlDsaSigner::new(&keys.sig_pq_secret_key, &keys.sig_pq_public_key)
+                .map_err(|e| CommunicationError::Other(e.to_string()))?;
+            let pq_signature = pq_signer
+                .sign(&sig_payload)
+                .map_err(|e| CommunicationError::Other(e.to_string()))?;
+            register =
+                register.add_typed_default(DataType::PqSignature, DataValue::Bytes(pq_signature));
+        }
+        /* ===== End Signature ===== */
+
         sender.send(&register).await?;
 
-        // 3. Receive host response
+        // 2. Receive host response (single message)
         let response = receiver.receive().await?;
 
         let connected = response.get_data(DataTypeId(11));
@@ -277,16 +316,36 @@ impl MTPClient {
             }
         };
 
+        let host_pq_sig = match response.get_data(DataTypeId(12)) {
+            DataValue::Bytes(b) => b.clone(),
+            _ => vec![],
+        };
+
         let mut host_sig_payload = Vec::new();
-        host_sig_payload.extend_from_slice(b"true");
-        host_sig_payload.extend_from_slice(&assigned_id.to_be_bytes());
+        host_sig_payload.push(0x01);
+        host_sig_payload.extend_from_slice(&(assigned_id as u64).to_be_bytes());
         host_sig_payload.extend_from_slice(&client_nonce.to_be_bytes());
         host_sig_payload.extend_from_slice(&host_new_nonce.to_be_bytes());
 
         /* ===== Signature ===== */
-        verify_ed25519(&host_public_key, &host_sig_payload, &host_sig).map_err(|_| {
-            CommunicationError::AuthenticationFailed("Host signature invalid".into())
-        })?;
+        verify_ed25519(
+            &host_public_key_bundle.sig_cl_public_key,
+            &host_sig_payload,
+            &host_sig,
+        )
+        .map_err(|_| CommunicationError::AuthenticationFailed("Host signature invalid".into()))?;
+        if !host_pq_sig.is_empty()
+            && verify_ml_dsa(
+                &host_public_key_bundle.sig_pq_public_key,
+                &host_sig_payload,
+                &host_pq_sig,
+            )
+            .is_err()
+        {
+            return Err(CommunicationError::AuthenticationFailed(
+                "Host PQ signature invalid".into(),
+            ));
+        }
         /* ===== End Signature ===== */
 
         Ok(MTPConnection {
@@ -298,4 +357,38 @@ impl MTPClient {
         })
     }
 }
-/* ===== End Authentication ===== */
+
+/* ================================ TESTS ================================ */
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_client_config_url() {
+        let config = ClientConfig {
+            url: "https://example.com:4433".into(),
+            server_cert: None,
+            client_id: 0,
+        };
+        assert_eq!(config.url, "https://example.com:4433");
+        assert!(config.server_cert.is_none());
+    }
+
+    #[test]
+    fn test_client_config_with_cert() {
+        let config = ClientConfig {
+            url: "https://localhost:4433".into(),
+            server_cert: Some(vec![0x01, 0x02, 0x03]),
+            client_id: 42,
+        };
+        assert_eq!(config.server_cert, Some(vec![0x01, 0x02, 0x03]));
+        assert_eq!(config.client_id, 42);
+    }
+
+    #[cfg(feature = "crypto")]
+    #[test]
+    fn test_auth_state_derive() {
+        assert_eq!(AuthState::Pending, AuthState::Pending);
+        assert_ne!(AuthState::Authenticated, AuthState::Failed);
+    }
+}
diff --git a/codec/src/communication_value.rs b/codec/src/communication_value.rs
index db3733c..0721398 100644
--- a/codec/src/communication_value.rs
+++ b/codec/src/communication_value.rs
@@ -7,10 +7,21 @@ use crate::data_value::DataValue;
 use crate::rand_u32;
 use mtp_common::CodecError;
 use mtp_type_map::{
-    communication_type_name, data_type_name, CommunicationType, CommunicationTypeId, DataType,
-    DataTypeId, TypeMap, PROTOCOL_VERSION,
+    CommunicationType, CommunicationTypeId, DataType, DataTypeId, PROTOCOL_VERSION, TypeMap,
+    communication_type_name, data_type_name,
 };
 
+#[cfg(feature = "crypto")]
+use mtp_crypto::SigAlgorithm;
+#[cfg(feature = "crypto")]
+use mtp_crypto::SignatureScheme;
+
+const FLAG_HAS_SENDER: u8 = 0b0000_0001;
+const FLAG_HAS_RECEIVER: u8 = 0b0000_0010;
+const FLAG_HAS_ID: u8 = 0b0000_0100;
+const FLAG_ENCRYPTED: u8 = 0b0000_1000;
+const FLAG_SIGNED: u8 = 0b0001_0000;
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct CommunicationValue {
     id: u32,
@@ -19,6 +30,8 @@ pub struct CommunicationValue {
     receiver: u64,
     data: BTreeMap<DataTypeId, DataValue>,
     type_map: Option<TypeMap>,
+    #[cfg(feature = "crypto")]
+    frame_signature: Option<(u8, Vec<u8>)>,
 }
 
 impl CommunicationValue {
@@ -33,6 +46,8 @@ impl CommunicationValue {
             receiver: 0,
             data: BTreeMap::new(),
             type_map: Some(tm),
+            #[cfg(feature = "crypto")]
+            frame_signature: None,
         }
     }
 
@@ -47,6 +62,8 @@ impl CommunicationValue {
             receiver: 0,
             data: BTreeMap::new(),
             type_map: Some(tm.clone()),
+            #[cfg(feature = "crypto")]
+            frame_signature: None,
         }
     }
 
@@ -107,63 +124,116 @@ impl CommunicationValue {
     pub fn get_data(&self, data_type: DataTypeId) -> &DataValue {
         self.data.get(&data_type).unwrap_or(&DataValue::Null)
     }
-
 }
 
 impl CommunicationValue {
     /*
      * Frame format (strict new format):
-     * [4 bytes u32 total_length] // number of bytes after this field
+     * [4 bytes u32 total_length]           // number of bytes after this field
      * [2 bytes u16 communication_type]
      * [1 byte flags]
-     * [optional 4 bytes id]      // if flags bit2 set
-     * [optional 6 bytes sender]  // if flags bit0 set
-     * [optional 6 bytes receiver]// if flags bit1 set
+     * [optional 4 bytes id]                // if flags bit2 set
+     * [optional 6 bytes sender]            // if flags bit0 set
+     * [optional 6 bytes receiver]          // if flags bit1 set
+     * [optional 1 byte signature type]     // if flags bit4 set; Type defines length of signature
+     * [optional signature]                 // if flags bit4 set
      * [data container bytes...]
      *
      * Flags:
      * bit0 => has sender
      * bit1 => has receiver
      * bit2 => has id
+     * bit3 => is data encrypted If so data bytes will be an encrypted container
+     * bit4 => is communication value signed
      */
     pub fn to_bytes(&self) -> Vec<u8> {
-        let mut payload = Vec::new();
-
         let has_sender = self.sender != 0;
         let has_receiver = self.receiver != 0;
         let has_id = self.id != 0;
 
+        #[cfg(feature = "crypto")]
+        let is_encrypted = self.data.len() == 1 && self.data.values().any(|v| {
+            matches!(
+                v,
+                DataValue::EncryptedContainer(_) | DataValue::SignedEncryptedContainer(_)
+            )
+        });
+        #[cfg(not(feature = "crypto"))]
+        let is_encrypted = false;
+
+        #[cfg(feature = "crypto")]
+        let has_frame_sig = self.frame_signature.is_some();
+        #[cfg(not(feature = "crypto"))]
+        let has_frame_sig = false;
+
         let mut flags: u8 = 0;
         if has_sender {
-            flags |= 0b0000_0001;
+            flags |= FLAG_HAS_SENDER;
         }
         if has_receiver {
-            flags |= 0b0000_0010;
+            flags |= FLAG_HAS_RECEIVER;
         }
         if has_id {
-            flags |= 0b0000_0100;
+            flags |= FLAG_HAS_ID;
+        }
+        if is_encrypted {
+            flags |= FLAG_ENCRYPTED;
+        }
+        if has_frame_sig {
+            flags |= FLAG_SIGNED;
         }
 
-        let _ = payload.write_u16::<BigEndian>(self.comm_type.0);
-        payload.push(flags);
+        let mut metadata = Vec::new();
+        let _ = metadata.write_u16::<BigEndian>(self.comm_type.0);
+        metadata.push(flags);
 
         if has_id {
-            let _ = payload.write_u32::<BigEndian>(self.id);
+            let _ = metadata.write_u32::<BigEndian>(self.id);
         }
 
         if has_sender {
             let sender_be = self.sender.to_be_bytes();
-            payload.extend_from_slice(&sender_be[2..]); // 6 bytes
+            metadata.extend_from_slice(&sender_be[2..]);
         }
 
         if has_receiver {
             let receiver_be = self.receiver.to_be_bytes();
-            payload.extend_from_slice(&receiver_be[2..]); // 6 bytes
+            metadata.extend_from_slice(&receiver_be[2..]);
         }
 
-        let container_value = DataValue::container_from_map(&self.data);
-        let container_bytes = container_value.to_bytes();
-        payload.extend_from_slice(&container_bytes);
+        #[cfg(feature = "crypto")]
+        let data_bytes = if is_encrypted {
+            self.data
+                .values()
+                .find_map(|v| match v {
+                    DataValue::EncryptedContainer(ct) => Some(ct.clone()),
+                    DataValue::SignedEncryptedContainer(ct) => Some(ct.clone()),
+                    _ => None,
+                })
+                .unwrap_or_default()
+        } else {
+            let container_value = DataValue::container_from_map(&self.data);
+            container_value.to_bytes()
+        };
+
+        #[cfg(not(feature = "crypto"))]
+        let data_bytes = {
+            let container_value = DataValue::container_from_map(&self.data);
+            container_value.to_bytes()
+        };
+
+        let mut payload = Vec::new();
+        payload.extend_from_slice(&metadata);
+
+        #[cfg(feature = "crypto")]
+        if let Some((_alg, _sig)) = &self.frame_signature {
+            // algorithm and signature are computed by sign_frame() and stored.
+            // The frame bytes are built by using the pre-computed signature.
+            payload.push(*_alg);
+            payload.extend_from_slice(_sig);
+        }
+
+        payload.extend_from_slice(&data_bytes);
 
         let mut frame = Vec::with_capacity(4 + payload.len());
         let _ = frame.write_u32::<BigEndian>(payload.len() as u32);
@@ -189,12 +259,17 @@ impl CommunicationValue {
             .map_err(|_| CodecError::InvalidEncoding)?;
         let comm_type = CommunicationTypeId(comm_type_num);
 
-        let flags = cursor
-            .read_u8()
-            .map_err(|_| CodecError::InvalidEncoding)?;
-        let has_sender = (flags & 0b0000_0001) != 0;
-        let has_receiver = (flags & 0b0000_0010) != 0;
-        let has_id = (flags & 0b0000_0100) != 0;
+        let flags = cursor.read_u8().map_err(|_| CodecError::InvalidEncoding)?;
+        let has_sender = (flags & FLAG_HAS_SENDER) != 0;
+        let has_receiver = (flags & FLAG_HAS_RECEIVER) != 0;
+        let has_id = (flags & FLAG_HAS_ID) != 0;
+        let is_encrypted = (flags & FLAG_ENCRYPTED) != 0;
+        let is_signed = (flags & FLAG_SIGNED) != 0;
+
+        #[cfg(not(feature = "crypto"))]
+        if is_signed || is_encrypted {
+            return Err(CodecError::InvalidEncoding);
+        }
 
         let id = if has_id {
             cursor
@@ -224,14 +299,47 @@ impl CommunicationValue {
             0
         };
 
+        #[cfg(feature = "crypto")]
+        let frame_signature = if is_signed {
+            let alg = cursor.read_u8().map_err(|_| CodecError::InvalidEncoding)?;
+            let sig_len =
+                SigAlgorithm::length(alg).ok_or(CodecError::InvalidEncoding)?;
+            let mut sig = vec![0u8; sig_len];
+            cursor
+                .read_exact(&mut sig)
+                .map_err(|_| CodecError::InvalidEncoding)?;
+            Some((alg, sig))
+        } else {
+            None
+        };
+
         let pos = cursor.position() as usize;
         if pos > frame_end {
             return Err(CodecError::InvalidEncoding);
         }
 
         let data_bytes = &bytes[pos..frame_end];
-        let data_value = DataValue::from_bytes(data_bytes).ok_or(CodecError::InvalidEncoding)?;
-        let data = data_value.as_map().ok_or(CodecError::InvalidEncoding)?;
+
+        #[cfg(feature = "crypto")]
+        let data = if is_encrypted {
+            let mut map = BTreeMap::new();
+            map.insert(
+                DataTypeId(0),
+                DataValue::EncryptedContainer(data_bytes.to_vec()),
+            );
+            map
+        } else {
+            let data_value =
+                DataValue::from_bytes(data_bytes).ok_or(CodecError::InvalidEncoding)?;
+            data_value.as_map().ok_or(CodecError::InvalidEncoding)?
+        };
+
+        #[cfg(not(feature = "crypto"))]
+        let data = {
+            let data_value =
+                DataValue::from_bytes(data_bytes).ok_or(CodecError::InvalidEncoding)?;
+            data_value.as_map().ok_or(CodecError::InvalidEncoding)?
+        };
 
         Ok(Self {
             id,
@@ -240,6 +348,8 @@ impl CommunicationValue {
             receiver,
             data,
             type_map: None,
+            #[cfg(feature = "crypto")]
+            frame_signature,
         })
     }
 
@@ -249,15 +359,129 @@ impl CommunicationValue {
         Ok(val)
     }
 
+    /*
+     * Sign the frame. Computes a signature over the canonical form:
+     *   comm_type || flags || id? || sender? || receiver? || data_bytes
+     *
+     * After calling this, `to_bytes()` will embed the algorithm and
+     * signature before the data payload.
+     */
+    #[cfg(feature = "crypto")]
+    pub fn sign_frame(
+        &mut self,
+        algorithm: u8,
+        signer: &impl SignatureScheme,
+    ) -> Option<()> {
+        let signed_payload = self.build_signed_payload();
+        let sig = signer.sign(&signed_payload).ok()?;
+        self.frame_signature = Some((algorithm, sig));
+        Some(())
+    }
+
+    /*
+     * Verify the frame signature. Reconstructs the signed payload from
+     * current state and checks it against the stored signature.
+     */
+    #[cfg(feature = "crypto")]
+    pub fn verify_frame(&self, verifier: &impl SignatureScheme) -> Result<(), CodecError> {
+        let (_algorithm, sig) = self
+            .frame_signature
+            .as_ref()
+            .ok_or(CodecError::InvalidEncoding)?;
+
+        let signed_payload = self.build_signed_payload();
+        verifier
+            .verify(&signed_payload, sig)
+            .map_err(|_| CodecError::InvalidEncoding)
+    }
+
+    /*
+     * Reconstruct the signed payload that the frame signature covers:
+     *   comm_type || flags || id? || sender? || receiver? || data_bytes
+     */
+    #[cfg(feature = "crypto")]
+    fn build_signed_payload(&self) -> Vec<u8> {
+        let has_sender = self.sender != 0;
+        let has_receiver = self.receiver != 0;
+        let has_id = self.id != 0;
+
+        let is_encrypted = self.data.len() == 1 && self.data.values().any(|v| {
+            matches!(
+                v,
+                DataValue::EncryptedContainer(_) | DataValue::SignedEncryptedContainer(_)
+            )
+        });
+
+        let mut flags: u8 = 0;
+        if has_sender {
+            flags |= FLAG_HAS_SENDER;
+        }
+        if has_receiver {
+            flags |= FLAG_HAS_RECEIVER;
+        }
+        if has_id {
+            flags |= FLAG_HAS_ID;
+        }
+        if is_encrypted {
+            flags |= FLAG_ENCRYPTED;
+        }
+        if self.frame_signature.is_some() {
+            flags |= FLAG_SIGNED;
+        }
+
+        let mut metadata = Vec::new();
+        let _ = metadata.write_u16::<BigEndian>(self.comm_type.0);
+        metadata.push(flags);
+
+        if has_id {
+            let _ = metadata.write_u32::<BigEndian>(self.id);
+        }
+
+        if has_sender {
+            let sender_be = self.sender.to_be_bytes();
+            metadata.extend_from_slice(&sender_be[2..]);
+        }
+
+        if has_receiver {
+            let receiver_be = self.receiver.to_be_bytes();
+            metadata.extend_from_slice(&receiver_be[2..]);
+        }
+
+        #[cfg(feature = "crypto")]
+        let data_bytes = if is_encrypted {
+            self.data
+                .values()
+                .find_map(|v| match v {
+                    DataValue::EncryptedContainer(ct) => Some(ct.clone()),
+                    DataValue::SignedEncryptedContainer(ct) => Some(ct.clone()),
+                    _ => None,
+                })
+                .unwrap_or_default()
+        } else {
+            let container_value = DataValue::container_from_map(&self.data);
+            container_value.to_bytes()
+        };
+
+        #[cfg(not(feature = "crypto"))]
+        let data_bytes = {
+            let container_value = DataValue::container_from_map(&self.data);
+            container_value.to_bytes()
+        };
+
+        [metadata, data_bytes].concat()
+    }
+
+    #[cfg(feature = "crypto")]
+    pub fn get_frame_signature(&self) -> Option<&(u8, Vec<u8>)> {
+        self.frame_signature.as_ref()
+    }
+
     #[cfg(feature = "registry")]
     pub fn migrate(&self, target_tm: &TypeMap) -> Result<Self, CodecError> {
-        let comm_name =
-            communication_type_name(self.comm_type.0).ok_or_else(|| {
-                CodecError::UnknownCommunicationType(self.comm_type.0.to_string())
-            })?;
-        let comm_variant = CommunicationType::from_name(comm_name).ok_or_else(|| {
-            CodecError::UnknownCommunicationType(comm_name.to_string())
-        })?;
+        let comm_name = communication_type_name(self.comm_type.0)
+            .ok_or_else(|| CodecError::UnknownCommunicationType(self.comm_type.0.to_string()))?;
+        let comm_variant = CommunicationType::from_name(comm_name)
+            .ok_or_else(|| CodecError::UnknownCommunicationType(comm_name.to_string()))?;
         let new_comm_id = CommunicationTypeId(
             target_tm
                 .comm_id_enum(comm_variant)
@@ -285,6 +509,8 @@ impl CommunicationValue {
             receiver: self.receiver,
             data: new_data,
             type_map: Some(target_tm.clone()),
+            #[cfg(feature = "crypto")]
+            frame_signature: self.frame_signature.clone(),
         })
     }
 }
diff --git a/codec/src/data_value.rs b/codec/src/data_value.rs
index bbe9fe4..9ad52c0 100644
--- a/codec/src/data_value.rs
+++ b/codec/src/data_value.rs
@@ -9,7 +9,7 @@ use std::io::Cursor;
 use mtp_type_map::DataTypeId;
 
 #[cfg(feature = "crypto")]
-use mtp_crypto::{AeadDecrypt, AeadEncrypt};
+use mtp_crypto::{AeadDecrypt, AeadEncrypt, SigAlgorithm, SignatureScheme};
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum DataKind {
@@ -27,6 +27,10 @@ pub enum DataKind {
 
     #[cfg(feature = "crypto")]
     EncryptedContainer,
+    #[cfg(feature = "crypto")]
+    SignedContainer,
+    #[cfg(feature = "crypto")]
+    SignedEncryptedContainer,
 
     Null,
 }
@@ -44,12 +48,47 @@ pub enum DataValue {
     Str(String),
     Bytes(Vec<u8>),
     Array(Vec<DataValue>),
-
+    /*
+     * Container format:
+     * [2 bytes u16 entry_count]       // number of entries
+     * [1 byte kind]                   // DataValue kind marker
+     * [if kind == BOOL_TRUE or BOOL_FALSE:]
+     *     [2 bytes u16 key]           // DataTypeId discriminant
+     * [else:]
+     *     [4 bytes u32 payload_len]   // length of the value payload
+     *     [2 bytes u16 key]           // DataTypeId discriminant
+     *     [payload_len bytes payload] // value data (interpreted based on kind)
+     */
     Container(Vec<(DataTypeId, DataValue)>),
 
+    /*
+     * Container format:
+     * [4 bytes u32 entry_count]       // length of the container
+     * [binary data]
+     * -> After decryption, the container is parsed as a regular container
+     */
     #[cfg(feature = "crypto")]
     EncryptedContainer(Vec<u8>),
 
+    /*
+     * Container format:
+     * [4 bytes u32 entry_count]       // length of the container
+     * [binary data]
+     * -> Can be turned into Container
+     * -> Can be used with a public key to verify integrity
+     */
+    #[cfg(feature = "crypto")]
+    SignedContainer(Vec<u8>),
+
+    /*
+     * Container format:
+     * [4 bytes u32 entry_count]       // length of the container
+     * [binary data]
+     * -> After decryption, the container is parsed as a signed container
+     */
+    #[cfg(feature = "crypto")]
+    SignedEncryptedContainer(Vec<u8>),
+
     Null,
 }
 
@@ -86,7 +125,9 @@ impl DataValue {
      * 0x08 => Array
      * 0x09 => Container
      * 0x0A => EncryptedContainer (4 bytes u32 len + encrypted bytes)
-     * 0x0B => Null
+     * 0x0B => SignedContainer (4 bytes u32 len + 3373 bytes signature)
+     * 0x0C => SignedEncryptedContainer (4 bytes u32 len + 3373 bytes signature + encrypted bytes)
+     * 0xFF => Null
      */
     const KIND_BOOL_TRUE: u8 = 0x01;
     const KIND_BOOL_FALSE: u8 = 0x02;
@@ -102,8 +143,12 @@ impl DataValue {
     const KIND_CONTAINER: u8 = 0x09;
     #[cfg(feature = "crypto")]
     const KIND_ENCRYPTED_CONTAINER: u8 = 0x0A;
+    #[cfg(feature = "crypto")]
+    const KIND_SIGNED_CONTAINER: u8 = 0x0B;
+    #[cfg(feature = "crypto")]
+    const KIND_SIGNED_ENCRYPTED_CONTAINER: u8 = 0x0C;
 
-    const KIND_NULL: u8 = 0x0B;
+    const KIND_NULL: u8 = 0xFF;
 
     pub fn container_from_map(map: &BTreeMap<DataTypeId, DataValue>) -> DataValue {
         let mut container = Vec::new();
@@ -131,6 +176,10 @@ impl DataValue {
             DataValue::Container(_) => DataKind::Container,
             #[cfg(feature = "crypto")]
             DataValue::EncryptedContainer(_) => DataKind::EncryptedContainer,
+            #[cfg(feature = "crypto")]
+            DataValue::SignedContainer(_) => DataKind::SignedContainer,
+            #[cfg(feature = "crypto")]
+            DataValue::SignedEncryptedContainer(_) => DataKind::SignedEncryptedContainer,
             DataValue::Null => DataKind::Null,
         }
     }
@@ -205,17 +254,29 @@ impl DataValue {
         }
     }
 
+    #[cfg(feature = "crypto")]
+    pub fn as_signed_container(&self) -> Option<Vec<u8>> {
+        match self {
+            DataValue::SignedContainer(b) => Some(b.clone()),
+            _ => None,
+        }
+    }
+
+    #[cfg(feature = "crypto")]
+    pub fn as_signed_encrypted_container(&self) -> Option<Vec<u8>> {
+        match self {
+            DataValue::SignedEncryptedContainer(c) => Some(c.clone()),
+            _ => None,
+        }
+    }
+
     /*
      * Decrypt an `EncryptedContainer` in-place, replacing it with the
      * deserialized `Container`. Returns `None` if decryption or
      * deserialization fails.
      */
     #[cfg(feature = "crypto")]
-    pub fn decrypt_into_container(
-        &mut self,
-        cipher: &impl AeadDecrypt,
-        aad: &[u8],
-    ) -> Option<()> {
+    pub fn decrypt_into_container(&mut self, cipher: &impl AeadDecrypt, aad: &[u8]) -> Option<()> {
         let data = self.as_encrypted_container()?;
         let plaintext = cipher.decrypt(&data, aad).ok()?;
         let dv = DataValue::from_bytes(&plaintext)?;
@@ -233,11 +294,7 @@ impl DataValue {
      * Returns `None` if the value is not a `Container` or encryption fails.
      */
     #[cfg(feature = "crypto")]
-    pub fn encrypt_container(
-        &mut self,
-        cipher: &impl AeadEncrypt,
-        aad: &[u8],
-    ) -> Option<()> {
+    pub fn encrypt_container(&mut self, cipher: &impl AeadEncrypt, aad: &[u8]) -> Option<()> {
         let entries = self.as_container()?;
         let plaintext = DataValue::Container(entries).to_bytes();
         let ct = cipher.encrypt(&plaintext, aad).ok()?;
@@ -245,6 +302,98 @@ impl DataValue {
         Some(())
     }
 
+    /*
+     * Sign a `Container` in-place, replacing it with a `SignedContainer`.
+     * The wire blob is: [1 byte alg] [N bytes sig] [serialized container bytes].
+     * The signature covers only the serialized container bytes (not the alg byte).
+     * Returns `None` if the value is not a `Container` or signing fails.
+     */
+    #[cfg(feature = "crypto")]
+    pub fn sign_container(
+        &mut self,
+        algorithm: u8,
+        signer: &impl SignatureScheme,
+    ) -> Option<()> {
+        let entries = self.as_container()?;
+        let container_bytes = Self::encode_container(&entries);
+
+        let sig = signer.sign(&container_bytes).ok()?;
+
+        let mut blob = Vec::with_capacity(1 + sig.len() + container_bytes.len());
+        blob.push(algorithm);
+        blob.extend_from_slice(&sig);
+        blob.extend_from_slice(&container_bytes);
+
+        *self = DataValue::SignedContainer(blob);
+        Some(())
+    }
+
+    /*
+     * Verify a `SignedContainer` in-place, replacing it with the deserialized
+     * `Container` on success. Returns `None` if verification fails or the
+     * blob is malformed.
+     */
+    #[cfg(feature = "crypto")]
+    pub fn verify_into_container(
+        &mut self,
+        verifier: &impl SignatureScheme,
+    ) -> Option<()> {
+        let blob = self.as_signed_container()?;
+        if blob.len() < 1 + 64 + 2 {
+            return None;
+        }
+
+        let algorithm = blob[0];
+        let sig_len = SigAlgorithm::length(algorithm)?;
+        if blob.len() < 1 + sig_len + 2 {
+            return None;
+        }
+
+        let signature = &blob[1..1 + sig_len];
+        let container_bytes = &blob[1 + sig_len..];
+
+        verifier.verify(container_bytes, signature).ok()?;
+
+        let entries = DataValue::from_bytes(container_bytes)?.as_container()?;
+        *self = DataValue::Container(entries);
+        Some(())
+    }
+
+    /*
+     * Encrypt a `Container` into a `SignedEncryptedContainer` in-place.
+     * The result is an opaque ciphertext that decrypts to a `SignedContainer`.
+     */
+    #[cfg(feature = "crypto")]
+    pub fn sign_and_encrypt_container(
+        &mut self,
+        algorithm: u8,
+        signer: &impl SignatureScheme,
+        cipher: &impl AeadEncrypt,
+        aad: &[u8],
+    ) -> Option<()> {
+        self.sign_container(algorithm, signer)?;
+        let blob = self.as_signed_container()?;
+        let ct = cipher.encrypt(&blob, aad).ok()?;
+        *self = DataValue::SignedEncryptedContainer(ct);
+        Some(())
+    }
+
+    /*
+     * Decrypt a `SignedEncryptedContainer` in-place, replacing it with a
+     * `SignedContainer`. Does NOT verify — call `verify_into_container` next.
+     */
+    #[cfg(feature = "crypto")]
+    pub fn decrypt_signed_encrypted_container(
+        &mut self,
+        cipher: &impl AeadDecrypt,
+        aad: &[u8],
+    ) -> Option<()> {
+        let data = self.as_signed_encrypted_container()?;
+        let plaintext = cipher.decrypt(&data, aad).ok()?;
+        *self = DataValue::SignedContainer(plaintext);
+        Some(())
+    }
+
     pub fn as_map(&self) -> Option<BTreeMap<DataTypeId, DataValue>> {
         match self {
             DataValue::Container(c) => {
@@ -311,7 +460,8 @@ impl DataValue {
         let kind = Self::kind_marker(value);
         buf.push(kind);
 
-        if kind == Self::KIND_BOOL_TRUE || kind == Self::KIND_BOOL_FALSE || kind == Self::KIND_NULL {
+        if kind == Self::KIND_BOOL_TRUE || kind == Self::KIND_BOOL_FALSE || kind == Self::KIND_NULL
+        {
             let _ = buf.write_u16::<BigEndian>(key.0);
             return true;
         }
@@ -351,7 +501,8 @@ impl DataValue {
         let kind = Self::kind_marker(value);
         buf.push(kind);
 
-        if kind == Self::KIND_BOOL_TRUE || kind == Self::KIND_BOOL_FALSE || kind == Self::KIND_NULL {
+        if kind == Self::KIND_BOOL_TRUE || kind == Self::KIND_BOOL_FALSE || kind == Self::KIND_NULL
+        {
             return true;
         }
 
@@ -414,6 +565,16 @@ impl DataValue {
                 buf.extend_from_slice(data);
                 Some(())
             }
+            #[cfg(feature = "crypto")]
+            DataValue::SignedContainer(data) => {
+                buf.extend_from_slice(data);
+                Some(())
+            }
+            #[cfg(feature = "crypto")]
+            DataValue::SignedEncryptedContainer(data) => {
+                buf.extend_from_slice(data);
+                Some(())
+            }
 
             DataValue::Null => Some(()),
         }
@@ -448,7 +609,10 @@ impl DataValue {
         for _ in 0..count {
             let kind = cursor.read_u8().ok()?;
 
-            if kind == Self::KIND_BOOL_TRUE || kind == Self::KIND_BOOL_FALSE || kind == Self::KIND_NULL {
+            if kind == Self::KIND_BOOL_TRUE
+                || kind == Self::KIND_BOOL_FALSE
+                || kind == Self::KIND_NULL
+            {
                 let key = DataTypeId(cursor.read_u16::<BigEndian>().ok()?);
                 let value = if kind == Self::KIND_BOOL_TRUE {
                     DataValue::BoolTrue
@@ -491,7 +655,10 @@ impl DataValue {
         for _ in 0..count {
             let kind = cursor.read_u8().ok()?;
 
-            if kind == Self::KIND_BOOL_TRUE || kind == Self::KIND_BOOL_FALSE || kind == Self::KIND_NULL {
+            if kind == Self::KIND_BOOL_TRUE
+                || kind == Self::KIND_BOOL_FALSE
+                || kind == Self::KIND_NULL
+            {
                 let value = if kind == Self::KIND_BOOL_TRUE {
                     DataValue::BoolTrue
                 } else if kind == Self::KIND_BOOL_FALSE {
@@ -609,9 +776,33 @@ impl DataValue {
                 cursor.set_position(end as u64);
                 Some(DataValue::EncryptedContainer(data))
             }
+            #[cfg(feature = "crypto")]
+            Self::KIND_SIGNED_CONTAINER => {
+                let len = payload_len?;
+                let start = cursor.position() as usize;
+                let end = start.checked_add(len)?;
+                if end > cursor.get_ref().len() {
+                    return None;
+                }
+                let data = cursor.get_ref()[start..end].to_vec();
+                cursor.set_position(end as u64);
+                Some(DataValue::SignedContainer(data))
+            }
+            #[cfg(feature = "crypto")]
+            Self::KIND_SIGNED_ENCRYPTED_CONTAINER => {
+                let len = payload_len?;
+                let start = cursor.position() as usize;
+                let end = start.checked_add(len)?;
+                if end > cursor.get_ref().len() {
+                    return None;
+                }
+                let data = cursor.get_ref()[start..end].to_vec();
+                cursor.set_position(end as u64);
+                Some(DataValue::SignedEncryptedContainer(data))
+            }
             Self::KIND_NULL => Some(DataValue::Null),
             #[cfg(not(feature = "crypto"))]
-            0x0A => None,
+            0x0A | 0x0B | 0x0C => None,
             _ => None,
         }
     }
@@ -636,6 +827,10 @@ impl DataValue {
             DataValue::Container(_) => Self::KIND_CONTAINER,
             #[cfg(feature = "crypto")]
             DataValue::EncryptedContainer(_) => Self::KIND_ENCRYPTED_CONTAINER,
+            #[cfg(feature = "crypto")]
+            DataValue::SignedContainer(_) => Self::KIND_SIGNED_CONTAINER,
+            #[cfg(feature = "crypto")]
+            DataValue::SignedEncryptedContainer(_) => Self::KIND_SIGNED_ENCRYPTED_CONTAINER,
             DataValue::Null => Self::KIND_NULL,
         }
     }
@@ -674,6 +869,10 @@ impl fmt::Display for DataValue {
             DataValue::Bytes(_) => write!(f, "(Binary)"),
             #[cfg(feature = "crypto")]
             DataValue::EncryptedContainer(_) => write!(f, "(Secure)"),
+            #[cfg(feature = "crypto")]
+            DataValue::SignedContainer(_) => write!(f, "(Signed)"),
+            #[cfg(feature = "crypto")]
+            DataValue::SignedEncryptedContainer(_) => write!(f, "(SignedSecure)"),
             DataValue::Null => write!(f, "null"),
         }
     }
@@ -696,6 +895,10 @@ impl PartialEq for DataValue {
             (Container(a), Container(b)) => a == b,
             #[cfg(feature = "crypto")]
             (EncryptedContainer(a), EncryptedContainer(b)) => a == b,
+            #[cfg(feature = "crypto")]
+            (SignedContainer(a), SignedContainer(b)) => a == b,
+            #[cfg(feature = "crypto")]
+            (SignedEncryptedContainer(a), SignedEncryptedContainer(b)) => a == b,
             (Null, Null) => true,
             _ => false,
         }
@@ -748,9 +951,408 @@ impl Hash for DataValue {
                 6u8.hash(state);
                 c.hash(state);
             }
-            Null => {
+            #[cfg(feature = "crypto")]
+            SignedContainer(c) => {
                 7u8.hash(state);
+                c.hash(state);
+            }
+            #[cfg(feature = "crypto")]
+            SignedEncryptedContainer(c) => {
+                8u8.hash(state);
+                c.hash(state);
+            }
+            Null => {
+                9u8.hash(state);
             }
         }
     }
 }
+
+/* ================================ TESTS ================================ */
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Only Container and Array can be top-level serialized forms.
+    /// Scalars must be tested inside a container.
+    fn container_roundtrip(values: Vec<(DataTypeId, DataValue)>) {
+        let dv = DataValue::Container(values.clone());
+        let bytes = dv.to_bytes();
+        let decoded = DataValue::from_bytes(&bytes).expect("roundtrip failed");
+        assert_eq!(dv, decoded, "container roundtrip mismatch");
+    }
+
+    fn array_roundtrip(values: Vec<DataValue>) {
+        let dv = DataValue::Array(values.clone());
+        let bytes = dv.to_bytes();
+        let decoded = DataValue::from_bytes(&bytes).expect("roundtrip failed");
+        assert_eq!(dv, decoded, "array roundtrip mismatch");
+    }
+
+    #[test]
+    fn test_bool_in_container() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::BoolTrue),
+            (DataTypeId(2), DataValue::BoolFalse),
+        ]);
+    }
+
+    #[test]
+    fn test_bool_true_eq() {
+        assert_eq!(DataValue::BoolTrue, DataValue::Bool(true));
+        assert_eq!(DataValue::BoolFalse, DataValue::Bool(false));
+        assert_ne!(DataValue::BoolTrue, DataValue::Bool(false));
+    }
+
+    #[test]
+    fn test_bool_as_bool() {
+        assert_eq!(DataValue::BoolTrue.as_bool(), Some(true));
+        assert_eq!(DataValue::BoolFalse.as_bool(), Some(false));
+        assert_eq!(DataValue::Bool(true).as_bool(), Some(true));
+        assert_eq!(DataValue::Null.as_bool(), None);
+    }
+
+    #[test]
+    fn test_signed_number_in_container() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::SignedNumber(0)),
+            (DataTypeId(2), DataValue::SignedNumber(42)),
+            (DataTypeId(3), DataValue::SignedNumber(-42)),
+            (DataTypeId(4), DataValue::SignedNumber(i128::MAX)),
+            (DataTypeId(5), DataValue::SignedNumber(i128::MIN)),
+        ]);
+    }
+
+    #[test]
+    fn test_unsigned_number_in_container() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::UnsignedNumber(0)),
+            (DataTypeId(2), DataValue::UnsignedNumber(42)),
+            (DataTypeId(3), DataValue::UnsignedNumber(u128::MAX)),
+        ]);
+    }
+
+    #[test]
+    fn test_float_in_container() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::Float(0, 0)),
+            (DataTypeId(2), DataValue::Float(2, 12345)),
+            (DataTypeId(3), DataValue::Float(255, 4294967295)),
+        ]);
+    }
+
+    #[test]
+    fn test_str_in_container() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::Str(String::new())),
+            (DataTypeId(2), DataValue::Str("hello".to_string())),
+            (DataTypeId(3), DataValue::Str("a".repeat(1000))),
+        ]);
+    }
+
+    #[test]
+    fn test_bytes_in_container() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::Bytes(vec![])),
+            (DataTypeId(2), DataValue::Bytes(vec![0x00, 0xFF, 0xAB])),
+            (DataTypeId(3), DataValue::Bytes(vec![0x42; 100])),
+        ]);
+    }
+
+    #[test]
+    fn test_null_in_container() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::Null),
+        ]);
+    }
+
+    #[test]
+    fn test_array_non_empty_roundtrip() {
+        array_roundtrip(vec![
+            DataValue::BoolTrue,
+            DataValue::SignedNumber(42),
+            DataValue::Str("hello".to_string()),
+            DataValue::Null,
+        ]);
+    }
+
+    #[test]
+    fn test_array_nested_roundtrip() {
+        array_roundtrip(vec![
+            DataValue::Array(vec![DataValue::BoolTrue, DataValue::BoolFalse]),
+            DataValue::Array(vec![DataValue::SignedNumber(1), DataValue::SignedNumber(2)]),
+        ]);
+    }
+
+    #[test]
+    fn test_container_empty_roundtrip() {
+        container_roundtrip(vec![]);
+    }
+
+    #[test]
+    fn test_container_mixed_roundtrip() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::BoolTrue),
+            (DataTypeId(2), DataValue::SignedNumber(-100)),
+            (DataTypeId(3), DataValue::Str("test".to_string())),
+            (DataTypeId(4), DataValue::UnsignedNumber(u128::MAX)),
+            (DataTypeId(5), DataValue::Null),
+        ]);
+    }
+
+    #[test]
+    fn test_container_nested_roundtrip() {
+        container_roundtrip(vec![
+            (DataTypeId(1), DataValue::Container(vec![
+                (DataTypeId(10), DataValue::BoolTrue),
+            ])),
+            (DataTypeId(2), DataValue::Array(vec![
+                DataValue::SignedNumber(1),
+                DataValue::SignedNumber(2),
+            ])),
+        ]);
+    }
+
+    #[test]
+    fn test_container_base64_roundtrip() {
+        let dv = DataValue::Container(vec![
+            (DataTypeId(7), DataValue::Bytes(vec![0xDE, 0xAD, 0xBE, 0xEF])),
+        ]);
+        let b64 = dv.to_base64();
+        let decoded = DataValue::from_base64(&b64).expect("base64 roundtrip failed");
+        assert_eq!(dv, decoded);
+    }
+
+    #[test]
+    fn test_kind_classification() {
+        assert_eq!(DataValue::BoolTrue.kind(), DataKind::Bool);
+        assert_eq!(DataValue::Bool(false).kind(), DataKind::Bool);
+        assert_eq!(DataValue::SignedNumber(0).kind(), DataKind::SignedNumber);
+        assert_eq!(DataValue::UnsignedNumber(0).kind(), DataKind::UnsignedNumber);
+        assert_eq!(DataValue::Float(0, 0).kind(), DataKind::Float);
+        assert_eq!(DataValue::Str(String::new()).kind(), DataKind::Str);
+        assert_eq!(DataValue::Bytes(vec![]).kind(), DataKind::Bytes);
+        assert_eq!(DataValue::Array(vec![]).kind(), DataKind::Array(Box::new(DataKind::Null)));
+        assert_eq!(DataValue::Container(vec![]).kind(), DataKind::Container);
+        assert_eq!(DataValue::Null.kind(), DataKind::Null);
+    }
+
+    #[test]
+    fn test_as_accessors() {
+        let dv = DataValue::Container(vec![
+            (DataTypeId(1), DataValue::Str("alice".to_string())),
+            (DataTypeId(2), DataValue::SignedNumber(42)),
+            (DataTypeId(3), DataValue::Bytes(vec![0x01, 0x02])),
+            (DataTypeId(4), DataValue::Array(vec![DataValue::BoolTrue])),
+        ]);
+
+        let map = dv.as_map().expect("should be a container");
+        assert_eq!(map.get(&DataTypeId(1)).and_then(|v| v.as_str()), Some("alice"));
+        assert_eq!(map.get(&DataTypeId(2)).and_then(|v| v.as_signed_number()), Some(42));
+        assert_eq!(map.get(&DataTypeId(3)).and_then(|v| v.as_bytes()), Some(vec![0x01, 0x02]));
+        assert_eq!(map.get(&DataTypeId(4)).and_then(|v| v.as_array()), Some(vec![DataValue::BoolTrue]));
+    }
+
+    #[test]
+    fn test_as_string() {
+        let dv = DataValue::Str("hello".to_string());
+        assert_eq!(dv.as_string(), Some("hello".to_string()));
+        assert_eq!(dv.as_str(), Some("hello"));
+        assert_eq!(DataValue::Null.as_string(), None);
+    }
+
+    #[test]
+    fn test_as_float() {
+        assert_eq!(DataValue::Float(3, 14).as_float(), Some((3, 14)));
+        assert_eq!(DataValue::Null.as_float(), None);
+    }
+
+    #[test]
+    fn test_container_from_map() {
+        let mut map = BTreeMap::new();
+        map.insert(DataTypeId(1), DataValue::BoolTrue);
+        map.insert(DataTypeId(2), DataValue::SignedNumber(99));
+        let dv = DataValue::container_from_map(&map);
+        let container = dv.as_container().expect("should be container");
+        assert_eq!(container.len(), 2);
+    }
+
+    #[test]
+    fn test_invalid_short_input() {
+        assert!(DataValue::from_bytes(&[]).is_none());
+        assert!(DataValue::from_bytes(&[0x01]).is_none());
+    }
+
+    #[test]
+    fn test_invalid_kind_rejected() {
+        let bytes = vec![0x00, 0x01, 0x0D, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x41];
+        assert!(DataValue::from_bytes(&bytes).is_none());
+    }
+
+    #[test]
+    fn test_truncated_container_rejected() {
+        let dv = DataValue::Container(vec![
+            (DataTypeId(1), DataValue::Str("hello".to_string())),
+        ]);
+        let bytes = dv.to_bytes();
+        // Truncate to fewer than 2 bytes so neither container nor array can be read
+        assert!(DataValue::from_bytes(&bytes[..1]).is_none());
+        assert!(DataValue::from_bytes(&bytes[..0]).is_none());
+    }
+
+    #[test]
+    fn test_display_basic() {
+        assert_eq!(format!("{}", DataValue::BoolTrue), "true");
+        assert_eq!(format!("{}", DataValue::BoolFalse), "false");
+        assert_eq!(format!("{}", DataValue::Null), "null");
+        assert_eq!(format!("{}", DataValue::SignedNumber(42)), "42");
+        assert_eq!(format!("{}", DataValue::UnsignedNumber(42)), "42");
+        assert_eq!(format!("{}", DataValue::Str("hi".to_string())), "\"hi\"");
+        assert_eq!(format!("{}", DataValue::Bytes(vec![])), "(Binary)");
+    }
+
+    #[test]
+    fn test_hash_consistency() {
+        use std::collections::HashSet;
+        let mut set = HashSet::new();
+        set.insert(DataValue::BoolTrue);
+        set.insert(DataValue::BoolFalse);
+        set.insert(DataValue::Null);
+        set.insert(DataValue::SignedNumber(1));
+        set.insert(DataValue::UnsignedNumber(1));
+        assert_eq!(set.len(), 5);
+        set.insert(DataValue::Bool(true));
+        assert_eq!(set.len(), 5);
+    }
+
+    #[test]
+    fn test_float_display() {
+        let s = format!("{}", DataValue::Float(2, 12345));
+        assert_eq!(s, "12345e2");
+    }
+
+    #[test]
+    fn test_container_display() {
+        let dv = DataValue::Container(vec![
+            (DataTypeId(3), DataValue::Str("v2.0".to_string())),
+            (DataTypeId(6), DataValue::UnsignedNumber(42)),
+        ]);
+        let s = format!("{}", dv);
+        assert!(s.contains("3:"));
+        assert!(s.contains("6:"));
+    }
+
+    #[test]
+    fn test_array_display() {
+        let dv = DataValue::Array(vec![DataValue::SignedNumber(1), DataValue::SignedNumber(2)]);
+        let s = format!("{}", dv);
+        assert_eq!(s, "[1, 2]");
+    }
+
+    /* ===== Crypto container tests ===== */
+
+    #[cfg(feature = "crypto")]
+    #[test]
+    fn test_encrypt_decrypt_container_roundtrip() {
+        use mtp_crypto::ChaCha20Poly1305;
+        let key = [0xAB; 32];
+        let cipher = ChaCha20Poly1305::new(key);
+
+        let mut dv = DataValue::Container(vec![
+            (DataTypeId(1), DataValue::Str("secret".to_string())),
+            (DataTypeId(2), DataValue::UnsignedNumber(42)),
+        ]);
+
+        assert!(dv.encrypt_container(&cipher, b"aad").is_some());
+        assert!(matches!(dv, DataValue::EncryptedContainer(_)));
+
+        assert!(dv.decrypt_into_container(&cipher, b"aad").is_some());
+        assert!(matches!(dv, DataValue::Container(_)));
+
+        let entries = dv.as_container().unwrap();
+        assert_eq!(entries.len(), 2);
+    }
+
+    #[cfg(feature = "crypto")]
+    #[test]
+    fn test_encrypt_container_wrong_key_fails() {
+        use mtp_crypto::ChaCha20Poly1305;
+        let cipher_a = ChaCha20Poly1305::new([0xAB; 32]);
+        let cipher_b = ChaCha20Poly1305::new([0xCD; 32]);
+
+        let mut dv = DataValue::Container(vec![
+            (DataTypeId(1), DataValue::Str("secret".to_string())),
+        ]);
+
+        assert!(dv.encrypt_container(&cipher_a, b"aad").is_some());
+        assert!(dv.decrypt_into_container(&cipher_b, b"aad").is_none());
+    }
+
+    #[cfg(feature = "crypto")]
+    #[test]
+    fn test_encrypt_container_wrong_aad_fails() {
+        use mtp_crypto::ChaCha20Poly1305;
+        let cipher = ChaCha20Poly1305::new([0xAB; 32]);
+
+        let mut dv = DataValue::Container(vec![
+            (DataTypeId(1), DataValue::Str("secret".to_string())),
+        ]);
+
+        assert!(dv.encrypt_container(&cipher, b"correct-aad").is_some());
+        assert!(dv.decrypt_into_container(&cipher, b"wrong-aad").is_none());
+    }
+
+    #[cfg(feature = "crypto")]
+    #[test]
+    fn test_encrypt_non_container_fails() {
+        let cipher = mtp_crypto::ChaCha20Poly1305::new([0xAB; 32]);
+
+        let mut dv = DataValue::Str("not a container".to_string());
+        assert!(dv.encrypt_container(&cipher, b"aad").is_none());
+    }
+
+    #[cfg(feature = "crypto")]
+    #[test]
+    fn test_sign_verify_container_roundtrip() {
+        use mtp_crypto::{ChaCha20Poly1305, Ed25519Signer, SigAlgorithm};
+
+        let (signer, sk, _pk) = Ed25519Signer::generate();
+        let cipher = ChaCha20Poly1305::new([0xAB; 32]);
+
+        let mut dv = DataValue::Container(vec![
+            (DataTypeId(1), DataValue::Str("signed data".to_string())),
+        ]);
+
+        assert!(dv
+            .sign_and_encrypt_container(SigAlgorithm::ED25519, &signer, &cipher, b"aad")
+            .is_some());
+        assert!(matches!(dv, DataValue::SignedEncryptedContainer(_)));
+
+        assert!(dv.decrypt_signed_encrypted_container(&cipher, b"aad").is_some());
+        assert!(matches!(dv, DataValue::SignedContainer(_)));
+
+        let verifier = Ed25519Signer::new(&sk).unwrap();
+        assert!(dv.verify_into_container(&verifier).is_some());
+        assert!(matches!(dv, DataValue::Container(_)));
+
+        let entries = dv.as_container().unwrap();
+        assert_eq!(entries.len(), 1);
+    }
+
+    #[cfg(feature = "crypto")]
+    #[test]
+    fn test_sign_container_wrong_key_fails() {
+        use mtp_crypto::{Ed25519Signer, SigAlgorithm};
+
+        let (signer, _, _) = Ed25519Signer::generate();
+        let (_, sk2, _) = Ed25519Signer::generate();
+        let wrong_verifier = Ed25519Signer::new(&sk2).unwrap();
+
+        let mut dv = DataValue::Container(vec![
+            (DataTypeId(1), DataValue::Str("signed data".to_string())),
+        ]);
+
+        assert!(dv.sign_container(SigAlgorithm::ED25519, &signer).is_some());
+        assert!(dv.verify_into_container(&wrong_verifier).is_none());
+    }
+}
diff --git a/common/src/lib.rs b/common/src/lib.rs
index 339d426..5cc7acc 100644
--- a/common/src/lib.rs
+++ b/common/src/lib.rs
@@ -18,8 +18,65 @@ pub enum CodecError {
     CryptoFailed(String),
 }
 
+/* ================================ TESTS ================================ */
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_codec_error_display() {
+        let e = CodecError::InvalidEncoding;
+        assert_eq!(format!("{}", e), "Invalid encoding");
+    }
+
+    #[test]
+    fn test_codec_error_unknown_version() {
+        assert_eq!(format!("{}", CodecError::UnknownVersion), "Unknown version");
+    }
+
+    #[test]
+    fn test_codec_error_clone_eq() {
+        let a = CodecError::InvalidEncoding;
+        let b = a.clone();
+        assert_eq!(a, b);
+    }
+
+    #[test]
+    fn test_communication_error_display() {
+        assert_eq!(format!("{}", CommunicationError::UseAfterClosed), "Use after Closed");
+        assert_eq!(format!("{}", CommunicationError::StreamClosed), "Stream Closed");
+        assert_eq!(format!("{}", CommunicationError::StreamError), "Stream Error");
+    }
+
+    #[test]
+    fn test_communication_error_clone() {
+        let a = CommunicationError::UseAfterClosed;
+        let b = a.clone();
+        assert_eq!(format!("{:?}", a), format!("{:?}", b));
+    }
+
+    #[test]
+    fn test_communication_error_authentication_failed() {
+        let e = CommunicationError::AuthenticationFailed("bad key".into());
+        assert!(format!("{}", e).contains("bad key"));
+    }
+
+    #[test]
+    fn test_communication_error_other() {
+        let e = CommunicationError::Other("custom error".into());
+        assert!(format!("{}", e).contains("custom error"));
+    }
+}
+
 #[derive(Debug, Error, Clone)]
 pub enum CommunicationError {
+    /* ====== NOTE on PartialEq ======
+     * Manual PartialEq implementation below compares some inner
+     * values (String, Vec<u8>) structurally and others only by
+     * variant discriminant (types from quinn / wtransport that
+     * don't themselves implement PartialEq).  Keep this impl in
+     * sync if variants are added or changed.
+     */
     #[error("Use after Closed")]
     UseAfterClosed,
 
@@ -89,3 +146,42 @@ pub enum CommunicationError {
     #[error("Other: {0}")]
     Other(String),
 }
+
+/* ===== Manual PartialEq =====
+ *
+ * Compare by variant, and structurally for String-holding variants.
+ * Third-party error types (quinn, wtransport) are compared only by
+ * discriminant since they don't implement PartialEq themselves.
+ */
+impl PartialEq for CommunicationError {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Self::UseAfterClosed, Self::UseAfterClosed) => true,
+            (Self::ClosedLocally, Self::ClosedLocally) => true,
+            (Self::ClosedByPeer, Self::ClosedByPeer) => true,
+            (Self::ConnectionLost, Self::ConnectionLost) => true,
+            (Self::Quinn(_), Self::Quinn(_)) => true,
+            (Self::ParseCommunicationValue, Self::ParseCommunicationValue) => true,
+            (Self::CertificateParseFailed, Self::CertificateParseFailed) => true,
+            (Self::CertificateLoadFailed, Self::CertificateLoadFailed) => true,
+            (Self::ParseError(a), Self::ParseError(b)) => a == b,
+            (Self::ConnectionError(_), Self::ConnectionError(_)) => true,
+            (Self::ConnectingError(a), Self::ConnectingError(b)) => a == b,
+            (Self::ReadToEndError(_), Self::ReadToEndError(_)) => true,
+            (Self::WriteError(_), Self::WriteError(_)) => true,
+            (Self::ClosedError(_), Self::ClosedError(_)) => true,
+            (Self::MessageTooLarge, Self::MessageTooLarge) => true,
+            (Self::ReadExactError(_), Self::ReadExactError(_)) => true,
+            (Self::StreamClosed, Self::StreamClosed) => true,
+            (Self::StreamError, Self::StreamError) => true,
+            (Self::StreamWriteError(_), Self::StreamWriteError(_)) => true,
+            (Self::StreamReadExactError(_), Self::StreamReadExactError(_)) => true,
+            (Self::CryptoProviderInstallFailed, Self::CryptoProviderInstallFailed) => true,
+            (Self::AuthenticationFailed(a), Self::AuthenticationFailed(b)) => a == b,
+            (Self::Other(a), Self::Other(b)) => a == b,
+            _ => false,
+        }
+    }
+}
+
+impl Eq for CommunicationError {}
diff --git a/crypto/Cargo.toml b/crypto/Cargo.toml
index b00a2fa..6a6cbd4 100644
--- a/crypto/Cargo.toml
+++ b/crypto/Cargo.toml
@@ -20,7 +20,9 @@ ml-dsa = { version = "0.1.1", optional = true }
 serde = { version = "1", optional = true, features = ["derive"] }
 
 [features]
-default = ["chacha20poly1305", "ed25519-dalek", "hkdf", "sha2"]
+default = ["chacha20poly1305", "ed25519-dalek", "hkdf", "sha2", "ml-dsa"]
+# Enabling ml-dsa by default ensures dual-signature support in the handshake
+# without requiring a separate PQC feature flag in host/client crates.
 full = ["default", "aes-gcm"]
 pqc = ["mlkem-tls", "ml-dsa"]
 serde = ["dep:serde"]
diff --git a/crypto/src/keypair.rs b/crypto/src/keypair.rs
index e7d87a5..bf41106 100644
--- a/crypto/src/keypair.rs
+++ b/crypto/src/keypair.rs
@@ -84,32 +84,6 @@ impl From<Vec<u8>> for SignaturePublicKey {
     }
 }
 
-#[derive(ZeroizeOnDrop)]
-pub struct KeyGroup {
-    #[zeroize(skip)]
-    pub encryption_public_key: EncryptionPublicKey,
-    pub encryption_private_key: EncryptionPrivateKey,
-    #[zeroize(skip)]
-    pub signature_public_key: SignaturePublicKey,
-    pub signature_private_key: SignaturePrivateKey,
-}
-
-impl KeyGroup {
-    pub fn new(
-        encryption_public_key: EncryptionPublicKey,
-        encryption_private_key: EncryptionPrivateKey,
-        signature_public_key: SignaturePublicKey,
-        signature_private_key: SignaturePrivateKey,
-    ) -> Self {
-        Self {
-            encryption_public_key,
-            encryption_private_key,
-            signature_public_key,
-            signature_private_key,
-        }
-    }
-}
-
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "serde", serde(transparent))]
 #[derive(Zeroize, ZeroizeOnDrop)]
diff --git a/crypto/src/lib.rs b/crypto/src/lib.rs
index 073d6e2..d132b63 100644
--- a/crypto/src/lib.rs
+++ b/crypto/src/lib.rs
@@ -11,6 +11,9 @@ pub mod kdf;
 #[cfg(any(feature = "ed25519-dalek", feature = "ml-dsa"))]
 pub mod sign;
 
+#[cfg(any(feature = "ed25519-dalek", feature = "ml-dsa"))]
+pub use sign::SigAlgorithm;
+
 #[cfg(feature = "mlkem-tls")]
 pub mod kem;
 
@@ -19,7 +22,7 @@ pub mod helper;
 pub use aead::{AeadCipher, AeadDecrypt, AeadEncrypt};
 pub use error::CryptoError;
 pub use keypair::{
-    EncryptionPrivateKey, EncryptionPublicKey, KemPrivateKey, KemPublicKey, KeyGroup, Keyring,
+    EncryptionPrivateKey, EncryptionPublicKey, KemPrivateKey, KemPublicKey, Keyring,
     PublicKeyBundle, SignaturePqPrivateKey, SignaturePqPublicKey, SignaturePrivateKey,
     SignaturePublicKey,
 };
diff --git a/crypto/src/sign.rs b/crypto/src/sign.rs
index aeb593f..c39bb55 100644
--- a/crypto/src/sign.rs
+++ b/crypto/src/sign.rs
@@ -3,6 +3,24 @@ use crate::error::CryptoError;
 #[cfg(feature = "ed25519-dalek")]
 use crate::keypair::{SignaturePrivateKey, SignaturePublicKey};
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct SigAlgorithm;
+
+impl SigAlgorithm {
+    pub const ED25519: u8 = 0x01;
+    pub const ML_DSA_65: u8 = 0x02;
+    pub const DUAL: u8 = 0x03;
+
+    pub const fn length(alg: u8) -> Option<usize> {
+        match alg {
+            Self::ED25519 => Some(64),
+            Self::ML_DSA_65 => Some(3309),
+            Self::DUAL => Some(3373),
+            _ => None,
+        }
+    }
+}
+
 #[cfg(feature = "ed25519-dalek")]
 use rand_core::RngCore;
 
diff --git a/example-usage/.gitignore b/example-usage/.gitignore
index cf5e6e3..11b7871 100644
--- a/example-usage/.gitignore
+++ b/example-usage/.gitignore
@@ -1,4 +1,6 @@
 client_keys.json
 host_keys.json
 host_sig_pk.bin
+host_sig_pq_pk.bin
+host_enc_kem_pk.bin
 clients.json
diff --git a/example-usage/client/Cargo.toml b/example-usage/client/Cargo.toml
index 1f2a829..b2c8193 100644
--- a/example-usage/client/Cargo.toml
+++ b/example-usage/client/Cargo.toml
@@ -1,16 +1,14 @@
 [package]
-name = "mtp-example-client"
+name = "client"
 version = "0.1.0"
 edition = "2024"
 
 [[bin]]
-name = "mtp-example-client"
+name = "client"
 path = "src/main.rs"
 
 [dependencies]
-mtp-client = { path = "../../client", features = ["crypto"] }
-mtp-codec = { path = "../../codec" }
-mtp-crypto = { path = "../../crypto" }
+mtp = { path = "../../", features = ["client", "crypto"] }
 tokio = { version = "1", features = ["full"] }
 serde_json = "1"
 hex = "0.4"
diff --git a/example-usage/client/src/main.rs b/example-usage/client/src/main.rs
index 88ed12e..fff8006 100644
--- a/example-usage/client/src/main.rs
+++ b/example-usage/client/src/main.rs
@@ -1,11 +1,10 @@
 use std::fs;
 
-use mtp_client::{ClientConfig, MTPClient, MTPConnection};
-use mtp_codec::{CommunicationType, CommunicationValue, DataType, DataValue};
-use mtp_crypto::{
-    Ed25519Signer, EncryptionPrivateKey, EncryptionPublicKey, KeyGroup, Keyring,
-    KemPrivateKey, KemPublicKey, SignaturePqPrivateKey, SignaturePqPublicKey,
-    SignaturePrivateKey, SignaturePublicKey,
+use mtp::client::{ClientConfig, MTPClient, MTPConnection};
+use mtp::codec::{CommunicationType, CommunicationValue, DataType, DataValue};
+use mtp::crypto::{
+    Ed25519Signer, KemPublicKey, Keyring, MlDsaSigner, PublicKeyBundle, SignaturePqPublicKey,
+    SignaturePublicKey,
 };
 
 /*
@@ -14,45 +13,39 @@ use mtp_crypto::{
  * connection and the local keyring.
  */
 async fn connect_or_register(
-    config: ClientConfig,
-    host_public_key: SignaturePublicKey,
+    mut config: ClientConfig,
+    host_public_key: PublicKeyBundle,
     client_key_path: &str,
 ) -> Result<(MTPConnection, Keyring), Box<dyn std::error::Error>> {
     if let Ok(data) = fs::read_to_string(client_key_path) {
         let json: serde_json::Value = serde_json::from_str(&data)?;
         let client_id = json["client_id"].as_u64().expect("Invalid client_id");
-        let keyring = Keyring::from_bytes(
-            &hex::decode(json["keyring"].as_str().expect("Missing keyring"))?,
-        )?;
+        let keyring = Keyring::from_bytes(&hex::decode(
+            json["keyring"].as_str().expect("Missing keyring"),
+        )?)?;
 
         println!("Loaded client keys (ID: {})", client_id);
 
-        let keygroup = KeyGroup::new(
-            EncryptionPublicKey::new(vec![]),
-            EncryptionPrivateKey::new(vec![]),
-            keyring.sig_cl_public_key.clone(),
-            SignaturePrivateKey::new(keyring.sig_cl_secret_key.as_bytes().to_vec()),
-        );
-
-        let conn = MTPClient::auth_connect(config, client_id, keygroup, host_public_key).await?;
+        config.client_id = client_id;
+        let conn = MTPClient::auth_connect(config, &keyring, &host_public_key).await?;
         println!("Authenticated (version {})", conn.version);
         Ok((conn, keyring))
     } else {
-        println!("No existing keys found - registering new client");
+        println!("No existing keys found: registering new client");
 
-        let (_signer, sig_sk, sig_pk) = Ed25519Signer::generate();
+        let (_ed_signer, sig_sk, sig_pk) = Ed25519Signer::generate();
+        let (_pq_signer, sig_pq_sk, sig_pq_pk) = MlDsaSigner::generate();
         let keyring = Keyring::new(
-            KemPublicKey::new(vec![]),
-            KemPrivateKey::new(vec![]),
-            SignaturePqPublicKey::new(vec![]),
-            SignaturePqPrivateKey::new(vec![]),
+            mtp::crypto::KemPublicKey::new(vec![]),
+            mtp::crypto::KemPrivateKey::new(vec![]),
+            sig_pq_pk,
+            sig_pq_sk,
             sig_pk,
             sig_sk,
         );
 
-        // Serialise before the move so we can persist and return the keyring
         let keyring_bytes = keyring.to_bytes();
-        let conn = MTPClient::auth_register(config, keyring, host_public_key).await?;
+        let conn = MTPClient::auth_register(config, &keyring, &host_public_key).await?;
         println!("Registered with ID: {}", conn.client_id);
 
         let json = serde_json::json!({
@@ -79,7 +72,10 @@ async fn send_ping_and_receive(conn: &MTPConnection) -> Result<(), Box<dyn std::
 
     let greeting = CommunicationValue::new(CommunicationType::Ping)
         .add_typed_default(DataType::Description, DataValue::Str("Hello MTP!".into()))
-        .add_typed_default(DataType::Timestamp, DataValue::UnsignedNumber(timestamp as u128))
+        .add_typed_default(
+            DataType::Timestamp,
+            DataValue::UnsignedNumber(timestamp as u128),
+        )
         .add_typed_default(DataType::Data, DataValue::UnsignedNumber(42))
         .with_sender(conn.client_id);
 
@@ -97,9 +93,17 @@ async fn send_ping_and_receive(conn: &MTPConnection) -> Result<(), Box<dyn std::
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let cert_pem = fs::read("server.pem").expect("Missing server.pem - run server first");
-    let host_public_key = SignaturePublicKey::new(
-        fs::read("host_sig_pk.bin").expect("Missing host_sig_pk.bin - run server first"),
+    let cert_pem = fs::read("server.pem").expect("Missing server.pem: run server first");
+    let host_public_key = PublicKeyBundle::new(
+        KemPublicKey::new(
+            fs::read("host_enc_kem_pk.bin").expect("Missing host_enc_kem_pk.bin: run server first"),
+        ),
+        SignaturePqPublicKey::new(
+            fs::read("host_sig_pq_pk.bin").expect("Missing host_sig_pq_pk.bin: run server first"),
+        ),
+        SignaturePublicKey::new(
+            fs::read("host_sig_pk.bin").expect("Missing host_sig_pk.bin: run server first"),
+        ),
     );
 
     println!("Connecting to 127.0.0.1:8080 ...");
@@ -107,6 +111,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let config = ClientConfig {
         url: "https://127.0.0.1:8080".into(),
         server_cert: Some(cert_pem),
+        client_id: 0,
     };
 
     let (conn, _keyring) = connect_or_register(config, host_public_key, "client_keys.json").await?;
diff --git a/example-usage/server/Cargo.toml b/example-usage/server/Cargo.toml
index 19f3031..79d33be 100644
--- a/example-usage/server/Cargo.toml
+++ b/example-usage/server/Cargo.toml
@@ -1,17 +1,16 @@
 [package]
-name = "mtp-example-server"
+name = "server"
 version = "0.1.0"
 edition = "2024"
 
 [[bin]]
-name = "mtp-example-server"
+name = "server"
 path = "src/main.rs"
 
 [dependencies]
-mtp-host = { path = "../../host", features = ["crypto"] }
-mtp-codec = { path = "../../codec" }
-mtp-crypto = { path = "../../crypto", features = ["serde"] }
+mtp = { path = "../../", features = ["crypto", "host"] }
 rcgen = "0.14"
 tokio = { version = "1", features = ["full"] }
-serde_json = "1"
+serde_json = { version = "1" }
 hex = "0.4"
+serde_core = "1.0.228"
diff --git a/example-usage/server/src/main.rs b/example-usage/server/src/main.rs
index b8aea9c..2d3b7a7 100644
--- a/example-usage/server/src/main.rs
+++ b/example-usage/server/src/main.rs
@@ -2,19 +2,19 @@ use std::collections::HashMap;
 use std::fs;
 use std::sync::{Arc, Mutex};
 
-use mtp_codec::{CommunicationType, CommunicationValue, DataType, DataTypeId, DataValue, TypeMap};
-use mtp_host::{HostConfig, MTPHost};
-use mtp_crypto::{
-    Ed25519Signer, KemPrivateKey, KemPublicKey, Keyring, PublicKeyBundle,
-    SignaturePqPrivateKey, SignaturePqPublicKey,
-};
+use mtp::codec::{CommunicationType, CommunicationValue, DataType, DataTypeId, DataValue, TypeMap};
+use mtp::crypto::{Ed25519Signer, Keyring, MlDsaSigner, PublicKeyBundle, kem::HybridKem};
+use mtp::host::{HostConfig, MTPHost};
 
 /*
  * Load an existing TLS certificate and key pair from disk.  If neither
  * file exists, generate a self-signed certificate so the server is
  * immediately usable without external tooling.
  */
-fn load_or_generate_tls(cert_path: &str, key_path: &str) -> Result<(Vec<u8>, Vec<u8>), Box<dyn std::error::Error>> {
+fn load_or_generate_tls(
+    cert_path: &str,
+    key_path: &str,
+) -> Result<(Vec<u8>, Vec<u8>), Box<dyn std::error::Error>> {
     if let (Ok(c), Ok(k)) = (fs::read(cert_path), fs::read(key_path)) {
         println!("Using existing TLS cert from {cert_path}");
         return Ok((c, k));
@@ -50,15 +50,10 @@ fn load_or_generate_host_keys(path: &str) -> Result<(u64, Keyring), Box<dyn std:
         return Ok((hid, keyring));
     }
 
-    let (_signer, sig_sk, sig_pk) = Ed25519Signer::generate();
-    let keyring = Keyring::new(
-        KemPublicKey::new(vec![]),
-        KemPrivateKey::new(vec![]),
-        SignaturePqPublicKey::new(vec![]),
-        SignaturePqPrivateKey::new(vec![]),
-        sig_pk,
-        sig_sk,
-    );
+    let (_ed_signer, sig_sk, sig_pk) = Ed25519Signer::generate();
+    let (_pq_signer, sig_pq_sk, sig_pq_pk) = MlDsaSigner::generate();
+    let (kem_sk, kem_pk) = HybridKem::generate_keypair();
+    let keyring = Keyring::new(kem_pk, kem_sk, sig_pq_pk, sig_pq_sk, sig_pk, sig_sk);
 
     let json = serde_json::json!({
         "host_id": 1,
@@ -76,20 +71,14 @@ fn load_or_generate_host_keys(path: &str) -> Result<(u64, Keyring), Box<dyn std:
  */
 fn load_client_db(
     path: &str,
-) -> Result<
-    (
-        Arc<Mutex<HashMap<u64, PublicKeyBundle>>>,
-        Arc<Mutex<u64>>,
-    ),
-    Box<dyn std::error::Error>,
-> {
-    let clients: Arc<Mutex<HashMap<u64, PublicKeyBundle>>> = Arc::new(Mutex::new(
-        if let Ok(data) = fs::read_to_string(path) {
+) -> Result<(Arc<Mutex<HashMap<u64, PublicKeyBundle>>>, Arc<Mutex<u64>>), Box<dyn std::error::Error>>
+{
+    let clients: Arc<Mutex<HashMap<u64, PublicKeyBundle>>> =
+        Arc::new(Mutex::new(if let Ok(data) = fs::read_to_string(path) {
             serde_json::from_str(&data).unwrap_or_default()
         } else {
             HashMap::new()
-        },
-    ));
+        }));
     let next_id = Arc::new(Mutex::new(
         clients.lock().unwrap().keys().max().unwrap_or(&999) + 1,
     ));
@@ -126,10 +115,15 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let (cert_pem, key_pem) = load_or_generate_tls("server.pem", "server.key")?;
     let (host_id, host_keyring) = load_or_generate_host_keys("host_keys.json")?;
 
-    // Export the host's Ed25519 public key so clients can verify it
+    // Export the host's public keys so clients can verify it
     fs::write(
-        "host_sig_pk.bin",
-        host_keyring.sig_cl_public_key.as_bytes(),
+        "host_enc_kem_pk.bin",
+        host_keyring.kem_public_key.as_bytes(),
+    )?;
+    fs::write("host_sig_pk.bin", host_keyring.sig_cl_public_key.as_bytes())?;
+    fs::write(
+        "host_sig_pq_pk.bin",
+        host_keyring.sig_pq_public_key.as_bytes(),
     )?;
 
     let (clients, next_id) = load_client_db("clients.json")?;
@@ -157,6 +151,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     println!("Starting MTP server on port 8080 ...");
 
     let config = HostConfig {
+        ip: std::net::IpAddr::V4(std::net::Ipv4Addr::UNSPECIFIED),
         port: 8080,
         tls_fullchain: cert_pem,
         tls_key: key_pem,
diff --git a/host/src/lib.rs b/host/src/lib.rs
index 6d6b24e..cbf0348 100644
--- a/host/src/lib.rs
+++ b/host/src/lib.rs
@@ -6,9 +6,11 @@ use mtp_codec::{
 };
 use mtp_common::CommunicationError;
 use mtp_transport::{Policy, Receiver, Sender};
+use std::net::IpAddr;
 
 // Host configuration.
 pub struct HostConfig {
+    pub ip: IpAddr,
     pub port: u16,
     pub tls_fullchain: Vec<u8>,
     pub tls_key: Vec<u8>,
@@ -60,6 +62,7 @@ impl MTPHost {
         let registry = Registry::builtin();
 
         let transport = mtp_transport::host(
+            config.ip,
             config.port,
             config.tls_fullchain.clone(),
             config.tls_key.clone(),
@@ -90,7 +93,7 @@ impl MTPHost {
             return self.accept_authenticated(sender, receiver).await;
         }
 
-        /* Read the first message (always encoded with reserved types). */
+        // Read the first message (always encoded with reserved types).
         let first_msg = receiver.receive().await.ok()?;
 
         /*
@@ -136,30 +139,12 @@ impl MTPHost {
         sender: Sender,
         receiver: Receiver,
     ) -> Option<MTPConnection> {
-        use mtp_crypto::{Ed25519Signer, PublicKeyBundle, SignatureScheme, verify_ed25519};
+        use mtp_crypto::{
+            Ed25519Signer, PublicKeyBundle, SignatureScheme, verify_ed25519, verify_ml_dsa,
+        };
 
-        // 1. Send host greeting
-        let host_nonce: u128 = rand::random();
-        let host_bundle = self.config.host_keyring.public_key_bundle();
-
-        let greeting =
-            CommunicationValue::new(mtp_codec::CommunicationType::IdentificationResponse)
-                .add_typed_default(
-                    DataType::Id,
-                    DataValue::UnsignedNumber(self.config.host_id as u128),
-                )
-                .add_typed_default(
-                    DataType::PublicKeys,
-                    DataValue::Bytes(host_bundle.as_bytes()),
-                )
-                .add_typed_default(DataType::ServerNonce, DataValue::UnsignedNumber(host_nonce));
-
-        sender.send(&greeting).await.ok()?;
-
-        // 2. Receive client message
+        // 1. Receive client message first (no host greeting)
         let msg = receiver.receive().await.ok()?;
-
-        // Extract common fields
         let version_str = match msg.get_data(DataTypeId(3)) {
             DataValue::Str(s) => s.clone(),
             _ => {
@@ -186,6 +171,11 @@ impl MTPHost {
             }
         };
 
+        let pq_sig_bytes: Vec<u8> = match msg.get_data(DataTypeId(12)) {
+            DataValue::Bytes(b) => b.clone(),
+            _ => vec![],
+        };
+
         let (assigned_id, client_bundle) = if msg.get_type() == mtp_codec::CommunicationTypeId(15) {
             // LOGIN
             let cid = match msg.get_data(DataTypeId(6)) {
@@ -231,12 +221,26 @@ impl MTPHost {
                 sender.close();
                 return None;
             }
+            if !pq_sig_bytes.is_empty()
+                && verify_ml_dsa(&bundle.sig_pq_public_key, &sig_payload, &pq_sig_bytes).is_err()
+            {
+                let rejection =
+                    CommunicationValue::new(mtp_codec::CommunicationType::IdentificationResponse)
+                        .add_typed_default(DataType::Connected, DataValue::BoolFalse)
+                        .add_typed_default(
+                            DataType::ClientNonce,
+                            DataValue::UnsignedNumber(client_nonce),
+                        );
+                let _ = sender.send(&rejection).await;
+                sender.close();
+                return None;
+            }
             /* ===== End Signature ===== */
 
             (cid, bundle)
-        } else if msg.get_type() == mtp_codec::CommunicationTypeId(14) {
+        } else if msg.get_type() == mtp_codec::CommunicationTypeId(17) {
             // REGISTER
-            let bundle = match msg.get_data(DataTypeId(8)) {
+            let bundle = match msg.get_data(DataTypeId(9)) {
                 DataValue::Bytes(b) => PublicKeyBundle::from_bytes(b).ok()?,
                 _ => {
                     sender.close();
@@ -263,6 +267,20 @@ impl MTPHost {
                 sender.close();
                 return None;
             }
+            if !pq_sig_bytes.is_empty()
+                && verify_ml_dsa(&bundle.sig_pq_public_key, &sig_payload, &pq_sig_bytes).is_err()
+            {
+                let rejection =
+                    CommunicationValue::new(mtp_codec::CommunicationType::RegisterResponse)
+                        .add_typed_default(DataType::Connected, DataValue::BoolFalse)
+                        .add_typed_default(
+                            DataType::ClientNonce,
+                            DataValue::UnsignedNumber(client_nonce),
+                        );
+                let _ = sender.send(&rejection).await;
+                sender.close();
+                return None;
+            }
             /* ===== End Signature ===== */
 
             let new_id = (self.config.complete_register)(bundle.clone());
@@ -272,11 +290,11 @@ impl MTPHost {
             return None;
         };
 
-        // 4. Send success response
+        // 2. Send success response (single host message)
         let new_nonce: u128 = rand::random();
 
         let mut host_sig_payload = Vec::new();
-        host_sig_payload.extend_from_slice(b"true");
+        host_sig_payload.push(0x01);
         host_sig_payload.extend_from_slice(&assigned_id.to_be_bytes());
         host_sig_payload.extend_from_slice(&client_nonce.to_be_bytes());
         host_sig_payload.extend_from_slice(&new_nonce.to_be_bytes());
@@ -285,9 +303,8 @@ impl MTPHost {
 
         /* ===== Signature ===== */
         let host_sig = host_signer.sign(&host_sig_payload).ok()?;
-        /* ===== End Signature ===== */
 
-        let response =
+        let mut response =
             CommunicationValue::new(mtp_codec::CommunicationType::IdentificationResponse)
                 .add_typed_default(DataType::Connected, DataValue::BoolTrue)
                 .add_typed_default(
@@ -298,9 +315,28 @@ impl MTPHost {
                 .add_typed_default(DataType::Signature, DataValue::Bytes(host_sig))
                 .add_typed_default(DataType::Id, DataValue::UnsignedNumber(assigned_id as u128));
 
+        if !self
+            .config
+            .host_keyring
+            .sig_pq_secret_key
+            .as_bytes()
+            .is_empty()
+        {
+            use mtp_crypto::MlDsaSigner;
+            let host_pq_signer = MlDsaSigner::new(
+                &self.config.host_keyring.sig_pq_secret_key,
+                &self.config.host_keyring.sig_pq_public_key,
+            )
+            .ok()?;
+            let host_pq_sig = host_pq_signer.sign(&host_sig_payload).ok()?;
+            response =
+                response.add_typed_default(DataType::PqSignature, DataValue::Bytes(host_pq_sig));
+        }
+        /* ===== End Signature ===== */
+
         sender.send(&response).await.ok()?;
 
-        // 5. Version negotiation
+        // 3. Version negotiation
         let negotiated = self.registry.negotiate(&[client_version])?;
         let codec = VersionedCodec::new(self.registry.clone());
 
diff --git a/transport/Cargo.toml b/transport/Cargo.toml
index d7ccda3..7e4d972 100644
--- a/transport/Cargo.toml
+++ b/transport/Cargo.toml
@@ -21,6 +21,9 @@ thiserror = "2.0.18"
 rustls-native-certs = "0.8.4"
 log = "0.4"
 
+[dev-dependencies]
+rcgen = "0.14"
+
 [features]
 default = []
 # Enables hosting a MTP server
diff --git a/transport/src/connection.rs b/transport/src/connection.rs
index 1738999..ed6bbd8 100644
--- a/transport/src/connection.rs
+++ b/transport/src/connection.rs
@@ -56,7 +56,6 @@ impl Default for Policy {
 enum ReceivedFrame {
     Message(CommunicationValue),
     ClosedByPeer,
-    #[allow(dead_code)]
     Idle,
 }
 
@@ -517,3 +516,48 @@ impl Receiver {
         self.handle.close_reason()
     }
 }
+
+/* ================================ TESTS ================================ */
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_send_mode_derive() {
+        assert_eq!(SendMode::PersistentStream, SendMode::PersistentStream);
+        assert_ne!(SendMode::PersistentStream, SendMode::SingleStreamPerMessage);
+    }
+
+    #[test]
+    fn test_policy_default_values() {
+        let p = Policy::default();
+        assert_eq!(p.send_mode, SendMode::PersistentStream);
+        assert_eq!(p.max_message_size, 1_000_000_000);
+        assert_eq!(p.close_frame_len, u32::MAX);
+        assert_eq!(p.application_close_code, 0);
+        assert_eq!(p.open_stream_timeout, Duration::from_millis(2_000));
+        assert_eq!(p.write_timeout, Duration::from_millis(2_000));
+        assert_eq!(p.accept_stream_timeout, Duration::from_millis(10_000));
+        assert_eq!(p.read_timeout, Duration::from_millis(30_000));
+        assert_eq!(p.keep_alive_interval, Some(Duration::from_secs(3)));
+        assert_eq!(p.max_idle_timeout, Some(Duration::from_secs(30)));
+        assert_eq!(p.force_close_delay, Duration::from_millis(300));
+        assert_eq!(p.max_transient_recv_errors, 20);
+        assert_eq!(p.transient_recv_backoff, Duration::from_millis(100));
+        assert_eq!(p.receiver_queue_capacity, 1000);
+    }
+
+    #[test]
+    fn test_policy_clone() {
+        let p = Policy::default();
+        let cloned = p.clone();
+        assert_eq!(p.send_mode, cloned.send_mode);
+    }
+
+    #[test]
+    fn test_policy_debug() {
+        let p = Policy::default();
+        let debug_str = format!("{:?}", p);
+        assert!(debug_str.contains("Policy"));
+    }
+}
diff --git a/transport/src/connection_handle.rs b/transport/src/connection_handle.rs
index 4ebe200..cbbbf2e 100644
--- a/transport/src/connection_handle.rs
+++ b/transport/src/connection_handle.rs
@@ -63,3 +63,70 @@ impl Default for ConnectionHandle {
         Self::new()
     }
 }
+
+/* ================================ TESTS ================================ */
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_new_is_open() {
+        let h = ConnectionHandle::new();
+        assert!(h.is_open());
+        assert!(!h.is_closed());
+    }
+
+    #[test]
+    fn test_close_transitions_state() {
+        let h = ConnectionHandle::new();
+        h.close(Some(CommunicationError::StreamClosed));
+        assert!(!h.is_open());
+        assert!(h.is_closed());
+    }
+
+    #[test]
+    fn test_close_reason_some() {
+        let h = ConnectionHandle::new();
+        h.close(Some(CommunicationError::UseAfterClosed));
+        assert!(h.close_reason().is_some());
+    }
+
+    #[test]
+    fn test_close_reason_none() {
+        let h = ConnectionHandle::new();
+        h.close(None);
+        assert!(h.close_reason().is_none());
+    }
+
+    #[test]
+    fn test_default_is_new() {
+        let h = ConnectionHandle::default();
+        assert!(h.is_open());
+    }
+
+    #[test]
+    fn test_close_with_error() {
+        let h = ConnectionHandle::new();
+        h.close_with_error(CommunicationError::MessageTooLarge);
+        assert!(h.is_closed());
+        assert!(h.close_reason().is_some());
+    }
+
+    #[test]
+    fn test_multiple_close_first_wins() {
+        let h = ConnectionHandle::new();
+        h.close(Some(CommunicationError::StreamClosed));
+        h.close(Some(CommunicationError::UseAfterClosed));
+        // First close reason is preserved
+        assert!(h.close_reason().is_some());
+    }
+
+    #[test]
+    fn test_close_sends_reason() {
+        let h = ConnectionHandle::new();
+        let mut rx = h.subscribe_close();
+        h.close(Some(CommunicationError::ClosedLocally));
+        // After close, the watch channel is updated
+        assert!(rx.borrow_and_update().is_some());
+    }
+}
diff --git a/transport/src/host.rs b/transport/src/host.rs
index d963fab..2274344 100644
--- a/transport/src/host.rs
+++ b/transport/src/host.rs
@@ -1,4 +1,5 @@
 use crate::{ConnectionHandle, Policy, Receiver, Sender};
+use log;
 use mtp_common::CommunicationError;
 use rustls::pki_types::{PrivateKeyDer, pem::PemObject};
 use std::net::{IpAddr, SocketAddr};
@@ -13,7 +14,13 @@ pub struct Host {
 
 impl Host {
     pub async fn next(&mut self) -> Option<(Sender, Receiver)> {
-        self.incoming.recv().await
+        log::warn!("[transport Host::next] waiting on recv...");
+        let result = self.incoming.recv().await;
+        match &result {
+            Some(_) => log::warn!("[transport Host::next] received connection"),
+            None => log::warn!("[transport Host::next] incoming channel closed - sender dropped"),
+        }
+        result
     }
 
     pub fn local_addr(&self) -> std::net::SocketAddr {
@@ -22,6 +29,7 @@ impl Host {
 }
 
 pub async fn host(
+    ip: IpAddr,
     port: u16,
     cert_pem: Vec<u8>,
     key_pem: Vec<u8>,
@@ -29,7 +37,7 @@ pub async fn host(
 ) -> Result<Host, CommunicationError> {
     let _ = rustls::crypto::aws_lc_rs::default_provider().install_default();
 
-    let server_config = configure_server(port, cert_pem, key_pem, &policy).await?;
+    let server_config = configure_server(ip, port, cert_pem, key_pem, &policy).await?;
     let endpoint = Endpoint::server(server_config)
         .map_err(|e| CommunicationError::Other(format!("Endpoint creation failed: {}", e)))?;
 
@@ -42,25 +50,37 @@ pub async fn host(
     let policy = Arc::new(policy);
 
     let task = tokio::spawn(async move {
+        log::warn!("[transport bg task] started");
         loop {
+            log::warn!("[transport bg task] waiting for connection...");
             let incoming_session = endpoint.accept().await;
+            log::warn!("[transport bg task] got incoming session");
 
             let request = match incoming_session.await {
-                Ok(req) => req,
-                Err(_) => {
+                Ok(req) => {
+                    log::warn!("[transport bg task] got request");
+                    req
+                }
+                Err(e) => {
+                    log::warn!("[transport bg task] incoming session error: {e}");
                     continue;
                 }
             };
 
             let connection = match request.accept().await {
-                Ok(conn) => conn,
-                Err(_) => {
+                Ok(conn) => {
+                    log::warn!("[transport bg task] connection accepted");
+                    conn
+                }
+                Err(e) => {
+                    log::warn!("[transport bg task] accept error: {e}");
                     continue;
                 }
             };
 
             let incoming_tx = incoming_tx.clone();
             let policy = policy.clone();
+            eprintln!("[transport bg task] spawning handle_connection");
             tokio::spawn(handle_connection(connection, incoming_tx, policy));
         }
     });
@@ -85,6 +105,7 @@ async fn handle_connection(
 }
 
 async fn configure_server(
+    bind_ip: IpAddr,
     port: u16,
     cert_pem: Vec<u8>,
     key_pem: Vec<u8>,
@@ -104,12 +125,6 @@ async fn configure_server(
 
     tls_config.alpn_protocols = vec![b"h3".to_vec()];
 
-    let bind_ip = std::env::var("mtp_BIND")
-        .ok()
-        .and_then(|s| if s.is_empty() { None } else { Some(s) })
-        .unwrap_or_else(|| "::".to_string())
-        .parse::<IpAddr>()
-        .map_err(|e| CommunicationError::ParseError(e.to_string()))?;
     let bind_addr = SocketAddr::new(bind_ip, port);
 
     let server_config = ServerConfig::builder()
diff --git a/transport/tests/integration.rs b/transport/tests/integration.rs
new file mode 100644
index 0000000..93377b3
--- /dev/null
+++ b/transport/tests/integration.rs
@@ -0,0 +1,174 @@
+use std::net::{IpAddr, Ipv4Addr};
+
+use mtp_transport::{Policy, host, connect};
+
+fn generate_self_signed_cert() -> (Vec<u8>, Vec<u8>) {
+    let key_pair = rcgen::KeyPair::generate().unwrap();
+    let params =
+        rcgen::CertificateParams::new(vec!["localhost".into(), "127.0.0.1".into()]).unwrap();
+    let cert = params.self_signed(&key_pair).unwrap();
+    let cert_pem = cert.pem();
+    let key_pem = key_pair.serialize_pem();
+    (cert_pem.into_bytes(), key_pem.into_bytes())
+}
+
+#[tokio::test]
+async fn test_host_start_and_stop() {
+    let (cert_pem, key_pem) = generate_self_signed_cert();
+    let h = host(
+        IpAddr::V4(Ipv4Addr::LOCALHOST),
+        0,
+        cert_pem,
+        key_pem,
+        Policy::default(),
+    )
+    .await
+    .unwrap();
+    let addr = h.local_addr();
+    // Port should be non-zero (OS-assigned)
+    assert!(addr.port() > 0);
+}
+
+#[tokio::test]
+async fn test_send_receive_roundtrip() {
+    let (cert_pem, key_pem) = generate_self_signed_cert();
+    let mut h = host(
+        IpAddr::V4(Ipv4Addr::LOCALHOST),
+        0,
+        cert_pem.clone(),
+        key_pem,
+        Policy::default(),
+    )
+    .await
+    .unwrap();
+    let addr = h.local_addr();
+
+    let url = format!("https://127.0.0.1:{}", addr.port());
+    let (client_tx, client_rx) =
+        connect(&url, Some(cert_pem), Policy::default()).await.unwrap();
+
+    // Accept on host side
+    let (host_tx, host_rx) = h.next().await.unwrap();
+
+    // Client sends a simple message
+    let msg = mtp_codec::CommunicationValue::new(mtp_codec::CommunicationType::Ping)
+        .add_data(
+            mtp_codec::DataTypeId(6),
+            mtp_codec::DataValue::UnsignedNumber(42),
+        );
+    client_tx.send(&msg).await.unwrap();
+
+    // Host receives it
+    let received = host_rx.receive().await.unwrap();
+    assert_eq!(received.get_type(), mtp_codec::CommunicationTypeId(19)); // Ping
+    let val = received.get_data(mtp_codec::DataTypeId(6)).clone();
+    assert_eq!(val, mtp_codec::DataValue::UnsignedNumber(42));
+
+    // Host sends a response
+    let resp = mtp_codec::CommunicationValue::new(mtp_codec::CommunicationType::Pong)
+        .add_data(
+            mtp_codec::DataTypeId(6),
+            mtp_codec::DataValue::UnsignedNumber(99),
+        );
+    host_tx.send(&resp).await.unwrap();
+
+    // Client receives it
+    let client_received = client_rx.receive().await.unwrap();
+    assert_eq!(client_received.get_type(), mtp_codec::CommunicationTypeId(20)); // Pong
+    let client_val = client_received.get_data(mtp_codec::DataTypeId(6)).clone();
+    assert_eq!(client_val, mtp_codec::DataValue::UnsignedNumber(99));
+
+    // Close both sides
+    client_tx.close();
+    host_tx.close();
+}
+
+#[tokio::test]
+async fn test_concurrent_messages() {
+    let (cert_pem, key_pem) = generate_self_signed_cert();
+    let mut h = host(
+        IpAddr::V4(Ipv4Addr::LOCALHOST),
+        0,
+        cert_pem.clone(),
+        key_pem,
+        Policy::default(),
+    )
+    .await
+    .unwrap();
+    let addr = h.local_addr();
+
+    let url = format!("https://127.0.0.1:{}", addr.port());
+    let (client_tx, _client_rx) =
+        connect(&url, Some(cert_pem), Policy::default()).await.unwrap();
+
+    let (_host_tx, host_rx) = h.next().await.unwrap();
+
+    // Send 5 messages in sequence
+    for i in 0..5u128 {
+        let msg = mtp_codec::CommunicationValue::new(mtp_codec::CommunicationType::Ping)
+            .add_data(
+                mtp_codec::DataTypeId(6),
+                mtp_codec::DataValue::UnsignedNumber(i),
+            );
+        client_tx.send(&msg).await.unwrap();
+    }
+
+    // Receive all 5 in order
+    for i in 0..5u128 {
+        let received = host_rx.receive().await.unwrap();
+        let val = received.get_data(mtp_codec::DataTypeId(6)).clone();
+        assert_eq!(val, mtp_codec::DataValue::UnsignedNumber(i));
+    }
+
+    // Send 3 responses back
+    for i in 0..3u128 {
+        let msg = mtp_codec::CommunicationValue::new(mtp_codec::CommunicationType::Pong)
+            .add_data(
+                mtp_codec::DataTypeId(6),
+                mtp_codec::DataValue::UnsignedNumber(i * 10),
+            );
+        client_tx.send(&msg).await.unwrap();
+    }
+
+    for i in 0..3u128 {
+        let received = host_rx.receive().await.unwrap();
+        let val = received.get_data(mtp_codec::DataTypeId(6)).clone();
+        assert_eq!(val, mtp_codec::DataValue::UnsignedNumber(i * 10));
+    }
+
+    client_tx.close();
+}
+
+#[tokio::test]
+async fn test_close_detection() {
+    let (cert_pem, key_pem) = generate_self_signed_cert();
+    let mut h = host(
+        IpAddr::V4(Ipv4Addr::LOCALHOST),
+        0,
+        cert_pem.clone(),
+        key_pem,
+        Policy::default(),
+    )
+    .await
+    .unwrap();
+    let addr = h.local_addr();
+
+    let url = format!("https://127.0.0.1:{}", addr.port());
+    let (client_tx, _client_rx) =
+        connect(&url, Some(cert_pem), Policy::default()).await.unwrap();
+
+    let (_host_tx, host_rx) = h.next().await.unwrap();
+
+    // Send a message then close
+    let msg = mtp_codec::CommunicationValue::new(mtp_codec::CommunicationType::Ping);
+    client_tx.send(&msg).await.unwrap();
+    client_tx.close();
+
+    // Host should still receive the message
+    let received = host_rx.receive().await.unwrap();
+    assert_eq!(received.get_type(), mtp_codec::CommunicationTypeId(19)); // Ping
+
+    // Host should get an error or closed signal on next receive
+    let result = host_rx.receive().await;
+    assert!(result.is_err());
+}
diff --git a/type-map/build.rs b/type-map/build.rs
index 8930db0..97b1a22 100644
--- a/type-map/build.rs
+++ b/type-map/build.rs
@@ -156,22 +156,28 @@ const RESERVED_DATA_TYPES: &[ReservedEntry] = &[
         name: "Connected",
         id: 11,
     },
+    ReservedEntry {
+        name: "PqSignature",
+        id: 12,
+    },
 ];
 
 fn main() {
     let out = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
     let multi_version = std::env::var("CARGO_FEATURE_REGISTRY").is_ok();
 
+    println!("cargo:rerun-if-env-changed=MTP_TYPE_MAPS");
+
     let config = match std::env::var("MTP_TYPE_MAPS") {
         Ok(config_path) => {
+            println!("cargo:rerun-if-changed={}", config_path);
+
             let content =
                 std::fs::read_to_string(&config_path).expect("Failed to read type-maps.yaml");
             serde_yaml::from_str(&content).expect("Failed to parse type-maps.yaml")
         }
         Err(_) => {
-            eprintln!(
-                "warning: MTP_TYPE_MAPS not set; generating types with reserved entries only"
-            );
+            eprint!("warning: MTP_TYPE_MAPS not set; generating types with reserved entries only");
             Config {
                 protocol_version: String::new(),
                 type_maps: BTreeMap::new(),
@@ -441,12 +447,7 @@ fn generate_data_type_enum(out: &mut String, user_names: &BTreeSet<&str>) {
         .unwrap();
     }
     for name in user_names {
-        writeln!(
-            out,
-            "            \"{}\" => Some(DataType::{}),",
-            name, name
-        )
-        .unwrap();
+        writeln!(out, "            \"{}\" => Some(DataType::{}),", name, name).unwrap();
     }
 
     writeln!(out, "            _ => None,").unwrap();
diff --git a/type-map/src/lib.rs b/type-map/src/lib.rs
index 29f5429..6bc5563 100644
--- a/type-map/src/lib.rs
+++ b/type-map/src/lib.rs
@@ -81,8 +81,8 @@ pub use registry::*;
 
 #[cfg(feature = "registry")]
 mod registry {
+    use crate::{TypeMap, Version, builtin_type_maps};
     use std::collections::BTreeMap;
-    use crate::{Version, TypeMap, builtin_type_maps};
 
     /*
      * Multi-version type-map registry.
@@ -142,6 +142,7 @@ mod registry {
         }
     }
 
+    /* ================================ TESTS ================================ */
     #[cfg(test)]
     mod tests {
         use super::*;