How can I get a PublicKey object from EC public key bytes?

Question

I am developing an application that needs to validate SHA256withECDSAsignatures with the help of secp256r1 (NIST P-256, P-256, prime256v1) public k

Answer 1

The Bouncy Castle example code on elliptic curve key pair Generation and key factories got me pretty close.

Once I managed to create a ECDSA key factory and a curve specification for the secp256r1/NIST P-256/P-256/prime256v1 curve I was able to use ECPointUtil.decodePoint to obtain a curve point. I could then generate a public key specification that enabled me to generate a public key like this:

private PublicKey getPublicKeyFromBytes(byte[] pubKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
    ECNamedCurveParameterSpec spec = ECNamedCurveTable.getParameterSpec("prime256v1");
    KeyFactory kf = KeyFactory.getInstance("ECDSA", new BouncyCastleProvider());
    ECNamedCurveSpec params = new ECNamedCurveSpec("prime256v1", spec.getCurve(), spec.getG(), spec.getN());
    ECPoint point =  ECPointUtil.decodePoint(params.getCurve(), pubKey);
    ECPublicKeySpec pubKeySpec = new ECPublicKeySpec(point, params);
    ECPublicKey pk = (ECPublicKey) kf.generatePublic(pubKeySpec);
    return pk;
}