Big Updated, added some tests, added comments for all functions, I forgot the rest

packages/crypto/src/worker.test.ts

@@ -0,0 +1,88 @@
+import { describe, expect, test } from "bun:test";
+import { x448 } from "@noble/curves/ed448.js";
+import { decrypt, encrypt, getSharedSecret } from "./worker";
+
+/**
+ * Encodes bytes to URL-safe base64 without padding.
+ * @param value Input bytes.
+ * @returns Base64url string.
+ */
+function bytesToB64u(value: Uint8Array): string {
+  const b64 = Buffer.from(value).toString("base64");
+  return b64.replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/g, "");
+}
+
+/**
+ * Converts bytes to lowercase hex.
+ * @param value Input bytes.
+ * @returns Hex string.
+ */
+function bytesToHex(value: Uint8Array): string {
+  return Array.from(value, (byte) => byte.toString(16).padStart(2, "0")).join(
+    "",
+  );
+}
+
+/**
+ * Creates deterministic 56-byte private key material for tests.
+ * @param seed Offset seed used to vary generated bytes.
+ * @returns Deterministic private key bytes.
+ */
+function createPrivateKey(seed: number): Uint8Array {
+  const output = new Uint8Array(56);
+
+  for (let index = 0; index < output.length; index += 1) {
+    output[index] = (seed + index) % 255;
+  }
+
+  return output;
+}
+
+describe("crypto worker", () => {
+  test("encrypt/decrypt round-trip returns original plaintext", async () => {
+    const secret = "a1".repeat(56);
+    const plaintext = "hello encrypted world";
+
+    const ciphertext = await encrypt(secret, plaintext);
+    const decrypted = await decrypt(secret, ciphertext);
+
+    expect(decrypted).toBe(plaintext);
+  });
+
+  test("decrypt fails with wrong shared secret", async () => {
+    const secret = "0f".repeat(56);
+    const wrongSecret = "f0".repeat(56);
+    const plaintext = "sensitive";
+
+    const ciphertext = await encrypt(secret, plaintext);
+
+    let failed = false;
+    try {
+      await decrypt(wrongSecret, ciphertext);
+    } catch {
+      failed = true;
+    }
+
+    expect(failed).toBe(true);
+  });
+
+  test("getSharedSecret matches noble x448 derivation", async () => {
+    const ownPrivateBytes = createPrivateKey(7);
+    const peerPrivateBytes = createPrivateKey(23);
+
+    const ownPublicBytes = x448.getPublicKey(ownPrivateBytes);
+    const peerPublicBytes = x448.getPublicKey(peerPrivateBytes);
+
+    const expected = bytesToHex(
+      new Uint8Array(x448.getSharedSecret(ownPrivateBytes, peerPublicBytes)),
+    );
+
+    const actual = await getSharedSecret(
+      bytesToB64u(ownPrivateBytes),
+      bytesToB64u(ownPublicBytes),
+      bytesToB64u(peerPublicBytes),
+    );
+
+    expect(actual).toBe(expected);
+  });
+});