chore: temp code for hmac debugging

packages/jwt-service/package.json

@@ -15,6 +15,8 @@
     "generate-plugin-schema": "sphereon dev generate-plugin-schema"
   },
   "dependencies": {
+    "@noble/curves": "1.7.0",
+    "@noble/hashes": "1.6.1",
     "@sphereon/ssi-sdk-ext.did-utils": "workspace:*",
     "@sphereon/ssi-sdk-ext.identifier-resolution": "workspace:*",
     "@sphereon/ssi-sdk-ext.key-manager": "workspace:*",

packages/jwt-service/src/agent/JwtService.ts

@@ -71,7 +71,7 @@ export class JwtService implements IAgentPlugin {
     try {
       debug(`JWE Encrypt: ${JSON.stringify(args, null, 2)}`)
 
-      let alg = jweAlg(args.alg) ?? jweAlg(protectedHeader.alg) ?? 'ECDH-ES'
+      const alg = jweAlg(args.alg) ?? jweAlg(protectedHeader.alg) ?? 'ECDH-ES'
       const enc = jweEnc(args.enc) ?? jweEnc(protectedHeader.enc) ?? 'A256GCM'
       const encJwks =
         recipientKey.jwks.length === 1

packages/jwt-service/src/functions/JWE.ts

@@ -17,6 +17,10 @@ import {
   JwsPayload,
 } from '../types/IJwtService'
 
+import { p256 } from '@noble/curves/p256'
+import { sha256 } from '@noble/hashes/sha256'
+import { hmac } from '@noble/hashes/hmac'
+
 export interface EncryptionResult {
   ciphertext: Uint8Array
   tag: Uint8Array
@@ -26,7 +30,6 @@ export interface EncryptionResult {
   cek?: Uint8Array
 }
 
-import {createHmac} from 'crypto';
 
 export const generateContentEncryptionKey = async ({
   alg,
@@ -249,12 +252,11 @@ export class CompactJwtEncrypter implements JweEncrypter {
     const iv = base64ToBytes(ivB64)
     const ciphertext = base64ToBytes(ciphertextB64)
 
-    // If this is a content encryption key, we can use it as the HMAC key
-    if (this.recipientKey instanceof Uint8Array) {
-      // Log the HMAC calculation
-      verifyHmac(iv, ciphertext, this.recipientKey)
+    if (this._alg?.startsWith('ECDH')) {
+      const derivedKey = await deriveEcdhKey(this.recipientKey as CryptoKey)
+      verifyHmacEcdh(iv, ciphertext, derivedKey)
     }
-
+    
     return jwt
   }
 
@@ -385,18 +387,43 @@ export function toWebCryptoCiphertext(ciphertext: string, tag: string): Uint8Arr
   return u8a.concat([base64ToBytes(ciphertext), base64ToBytes(tag)])
 }
 
-function verifyHmac(iv: Uint8Array, ciphertext: Uint8Array, macKey: Uint8Array) {
-  const hmac = createHmac('sha256', macKey)
-  hmac.update(new Uint8Array([...iv, ...ciphertext]))
-  const computedHash = hmac.digest()
 
-  console.log('Computed HMAC:', u8a.toString(computedHash, 'hex'))
-
-  // Here, replace `expectedAuthTag` with the actual authentication tag from the JWE
-  const expectedAuthTag = new Uint8Array() // Placeholder, replace with actual value
-  if (u8a.equals(computedHash, expectedAuthTag)) {
-    console.log('HMAC verification succeeded!')
-  } else {
-    console.error('HMAC verification failed!')
+async function deriveEcdhKey(publicKey: CryptoKey): Promise<Uint8Array> {
+  // Extract public key coordinates
+  const jwk = await crypto.subtle.exportKey('jwk', publicKey)
+  if (!jwk.x || !jwk.y) {
+    throw new Error('Invalid public key format')
   }
+
+  // Convert base64url coordinates to bytes
+  const xBytes = base64ToBytes(jwk.x)
+  const yBytes = base64ToBytes(jwk.y)
+
+  // Create point from coordinates
+  const point = p256.ProjectivePoint.fromAffine({
+    x: BigInt('0x' + u8a.toString(xBytes, 'hex')),
+    y: BigInt('0x' + u8a.toString(yBytes, 'hex'))
+  })
+
+  // Generate ephemeral key pair
+  const ephemeralPrivate = p256.utils.randomPrivateKey()
+  //const ephemeralPoint = p256.getPublicKey(ephemeralPrivate)
+
+  // Compute shared secret
+  const sharedPoint = point.multiply(BigInt('0x' + u8a.toString(ephemeralPrivate, 'hex')))
+  const sharedSecret = u8a.fromString(sharedPoint.x.toString(16), 'hex')
+
+  // Derive key using concat KDF as per JOSE spec
+  const derivedKey = await crypto.subtle.digest('SHA-256', sharedSecret)
+
+  return new Uint8Array(derivedKey)
+}
+
+function verifyHmacEcdh(iv: Uint8Array, ciphertext: Uint8Array, derivedKey: Uint8Array) {
+  const hmacKey = hmac.create(sha256, derivedKey)
+  const data = new Uint8Array([...iv, ...ciphertext])
+  const computedHmac = hmacKey.update(data).digest()
+
+  console.log('ECDH Derived Key:', u8a.toString(derivedKey, 'hex'))
+  console.log('Computed HMAC:', u8a.toString(computedHmac, 'hex'))
 }