ecdh test

package.json

@@ -9,6 +9,7 @@
   "author": "Sam Hadow",
   "license": "BSD-3-Clause-Attribution",
   "dependencies": {
+    "@noble/curves": "^1.8.1",
     "bootstrap": "^5.3.3",
     "connect-sqlite3": "^0.9.15",
     "cookie-parser": "^1.4.7",

src/public/ecdh.js

@@ -0,0 +1,15 @@
+// X25519 aka ECDH on Curve25519 from [RFC7748](https://www.rfc-editor.org/rfc/rfc7748)
+import { x25519 } from '@noble/curves/ed25519';
+
+export function genKeys() {
+    const priv = x25519.utils.randomPrivateKey();
+    const pub = x25519.getPublicKey(priv);
+    return {
+        privkey: priv,
+        pubkey: pub
+    };
+}
+
+export function sharedKey(priv, pub) {
+    return x25519.getSharedSecret(priv, pub);
+}

tests/ecdh.test.js

@@ -0,0 +1,16 @@
+import { genKeys, sharedKey } from '../src/public/ecdh.js';
+import { arrayToHex } from '../src/stringutils.js';
+
+describe('ecdh.js functions', () => {
+
+    it('key exchange test', () => {
+        const keysA= genKeys();
+        const keysB = genKeys();
+        const sharedA = sharedKey(keysA.privkey, keysB.pubkey);
+        const sharedB = sharedKey(keysB.privkey, keysA.pubkey);
+        const sharedAhex = arrayToHex(sharedA);
+        const sharedBhex = arrayToHex(sharedB);
+        expect(sharedAhex === sharedBhex);
+    });
+
+});