Topic: [SOLVED] Java/BouncyCastle - How to create public key with x and y coordinates? (Read 8808 times)

Thank you #dirtyfilthy. I have been finding this for a while. Your solution is working. This piece of code is helping me injecting the generated public key from HSM into JCE. Somehow the sample on the boucny castle website is buggy. I hope this can help other ppl who needs importing the public key into JCE.

Cheers

Is this a bitcoin signature? Because the bitcoin signature has one byte tacked on to the end that you need to remove (the hashtype) before verifying.

Hey,

So you said you wouldn't mind answering any question regarding this-

So I've been working on a project and I need to verify a signature, given to me.

When I both generate & verify the signature, everything works perfectly, but when I'm trying to verify the other guy's signature it crushes saying: "error decoding signature bytes.", specifically I found out it crushes here:
ASN1InputStream aIn = new ASN1InputStream(signature.getBytes());
try {
       ASN1Sequence s = (ASN1Sequence)aIn.readObject();/*crushes on this line exactly...*/
} catch (IOException e) {

}

I attached the functions related...

private PublicKey generatePublicKey(Point pPublicKey, String sCurve)
         throws IOException, NoSuchAlgorithmException,
         NoSuchProviderException, InvalidKeySpecException,
         InvalidAlgorithmParameterException {
       X9ECParameters ecParams = NISTNamedCurves.getByName(sCurve);
       ECPoint pPublicPoint = ecParams.getCurve().createPoint(pPublicKey.x,
       pPublicKey.y, false);
       ECParameterSpec spec = new ECParameterSpec(ecParams.getCurve(),
       ecParams.getG(), ecParams.getN());
       ECPublicKeySpec publicSpec = new ECPublicKeySpec(pPublicPoint, spec);
       KeyFactory keyfac = KeyFactory.getInstance("ECDSA", "LOCAL_BC");
       return keyfac.generatePublic(publicSpec);
   }

   public ECDSAVerifier(Point pKey, String sHash, String sCurve)
         throws InvalidKeyException, NoSuchAlgorithmException,
         NoSuchProviderException, InvalidKeySpecException, IOException,
         InvalidAlgorithmParameterException {
      this.key = generatePublicKey(pKey, sCurve);
      this.hashName = sHash;
      ECDSAGenerateVerifier();
   }

   private void ECDSAGenerateVerifier() throws NoSuchAlgorithmException,
         NoSuchProviderException, InvalidKeyException {
      this.verifier = Signature.getInstance(this.hashName, "LOCAL_BC");
      this.verifier.initVerify(this.key);
   }

   public Boolean verify(byte[] message, byte[] signature)
         throws SignatureException, InvalidKeyException {
      this.verifier.update(message);
      return this.verifier.verify(signature); /*the code crushes here...*/
   }

Works perfectly! Thank you very much!

public static ECPublicKey decodeKey(byte[] encoded) throws InvalidKeySpecException, NoSuchAlgorithmException, NoSuchProviderException{
    ECNamedCurveParameterSpec params = ECNamedCurveTable.getParameterSpec("secp256k1");
    KeyFactory fact = KeyFactory.getInstance("ECDSA", "BC");
    ECCurve curve = params.getCurve();
    java.security.spec.EllipticCurve ellipticCurve = EC5Util.convertCurve(curve, params.getSeed());
    java.security.spec.ECPoint point=ECPointUtil.decodePoint(ellipticCurve, encoded);
    java.security.spec.ECParameterSpec params2=EC5Util.convertSpec(ellipticCurve, params);
    java.security.spec.ECPublicKeySpec keySpec = new java.security.spec.ECPublicKeySpec(point,params2);
    return (ECPublicKey) fact.generatePublic(keySpec);
}

I'm implementation an android client at the moment and would be happy to chat re: any question you have.

Regards, etc.

From the wiki (https://en.bitcoin.it/wiki/Protocol_specification#Signatures):
I'm using the Java version of the BouncyCastle crypto library, and between the Java crypto classes and the BouncyCastle crypto classes, I can't figure out how I can create a public key object with the x and y coordinates.

Does anyone have any idea how I would go about this?

I'm correct in needing to use these coordinates to create a public key object to use for verifying signatures, right?