(feat): crypto migrations

src/sdk/ratchet.ts

@@ -0,0 +1,70 @@
+import * as bindings from "mtp/raw";
+
+function utf8Encode(text: string): Uint8Array {
+  if (typeof TextEncoder !== "undefined") {
+    return new TextEncoder().encode(text);
+  }
+  if (typeof Buffer !== "undefined") {
+    return new Uint8Array(Buffer.from(text, "utf-8"));
+  }
+  const bytes = new Uint8Array(text.length * 4);
+  let len = 0;
+  for (let i = 0; i < text.length; i += 1) {
+    const code = text.codePointAt(i) as number;
+    if (code < 0x80) {
+      bytes[len++] = code;
+    } else if (code < 0x800) {
+      bytes[len++] = 0xc0 | (code >> 6);
+      bytes[len++] = 0x80 | (code & 0x3f);
+    } else if (code < 0x10000) {
+      bytes[len++] = 0xe0 | (code >> 12);
+      bytes[len++] = 0x80 | ((code >> 6) & 0x3f);
+      bytes[len++] = 0x80 | (code & 0x3f);
+    } else {
+      bytes[len++] = 0xf0 | (code >> 18);
+      bytes[len++] = 0x80 | ((code >> 12) & 0x3f);
+      bytes[len++] = 0x80 | ((code >> 6) & 0x3f);
+      bytes[len++] = 0x80 | (code & 0x3f);
+      i += 1;
+    }
+  }
+  return bytes.subarray(0, len);
+}
+
+const HKDF_MESSAGE_KEY = "mtp-e2ee-v1-message-key";
+const HKDF_NEXT_CHAIN = "mtp-e2ee-v1-next-chain";
+
+export interface RatchetStep {
+  key: Uint8Array;
+  chainKey: Uint8Array;
+}
+
+export class MTPRatchet {
+  static async stepSend(chainKey: Uint8Array): Promise<RatchetStep> {
+    return this.step(chainKey);
+  }
+
+  static async stepRecv(chainKey: Uint8Array): Promise<RatchetStep> {
+    return this.step(chainKey);
+  }
+
+  static async step(chainKey: Uint8Array): Promise<RatchetStep> {
+    const messageKey = bindings.wasm_hkdf_expand(
+      chainKey,
+      new Uint8Array(0),
+      utf8Encode(HKDF_MESSAGE_KEY),
+      32,
+    );
+    const nextChainKey = bindings.wasm_hkdf_expand(
+      chainKey,
+      new Uint8Array(0),
+      utf8Encode(HKDF_NEXT_CHAIN),
+      32,
+    );
+
+    return {
+      key: messageKey,
+      chainKey: nextChainKey,
+    };
+  }
+}