add PublicSigningKey.fromSignedEthereumMessage fn

mediachain · Jan 18, 2017 · 36a5ca1 · 36a5ca1
1 parent 3edfe39
commit 36a5ca1
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diff --git a/src/peer/identity.js b/src/peer/identity.js
@@ -179,6 +179,17 @@ class PublicSigningKey {
     }
   }
 
+  static fromSignedEthereumMessage (message: Buffer, signature: Buffer, ethereumAddress: Buffer | string): PublicSigningKey {
+    const pubKey = recoverEthereumPubKey(message, signature)
+    const addrForSig = ethereumUtils.pubToAddress(pubKey, true)
+    const expectedAddr = ethereumUtils.toBuffer(ethereumAddress)
+    if (!expectedAddr.equals(addrForSig)) {
+      throw new Error(`Public key for signature does not match expected ethereum address ${expectedAddr.toString('hex')}`)
+    }
+    const p2pKey = new Secp256k1PublicKey(pubKey)
+    return new PublicSigningKey(p2pKey)
+  }
+
   get isSecp256k1 () {
     return (this._key instanceof Secp256k1PublicKey)
   }

diff --git a/test/signature_test.js b/test/signature_test.js
@@ -109,4 +109,11 @@ describe('Signature verification', () => {
         assert(valid, 'signature verification failed')
       })
   })
+
+  it('recovers a PublicSigningKey from a signed ethereum message and account address', () => {
+    const {message, signature, ethAccount, ethPubKey} = ETH_MESSAGE_FIXTURES
+    const pubKey = PublicSigningKey.fromSignedEthereumMessage(message, signature, ethAccount)
+    const keyFromHex = PublicSigningKey.fromBytes(ethPubKey)
+    assert.deepEqual(pubKey.bytes, keyFromHex.bytes, 'public key recovery failed')
+  })
 })