如何使用FIPS BouncyCastle将ECPrivateKey转换为ECPublicKey？

Question

如何使用FIPS BouncyCastle将ECPrivateKey转换为ECPublicKey？

我使用以下代码（略有简化）将ECPrivateKey转换为ECPublicKey：

public static ECPublicKey getPublicKeyFromPrivateKey(ECPrivateKey privateKey) throws GeneralSecurityException {
    final KeyFactory keyFactory = KeyFactory.getInstance("ECDSA", new BouncyCastleProvider());
    final BCECPrivateKey bcecPrivateKey = (BCECPrivateKey) privateKey;
    final ECParameterSpec ecSpec = bcecPrivateKey.getParameters();
    final ECPoint q = ecSpec.getG().multiply(bcecPrivateKey.getD());
    final byte[] qBytes = q.getEncoded(false);
    final ECPoint point = ecSpec.getCurve().decodePoint(qBytes);
    final ECPublicKeySpec pubSpec = new ECPublicKeySpec(point, ecSpec);
    return (ECPublicKey) keyFactory.generatePublic(pubSpec);
}

与非FIPS BouncyCastle配合使用时效果很好。现在，我们需要以符合FIPS的方式做同样的事情。这里的问题是FIPS BouncyCastle 1.0.1中似乎不存在ECParameterSpec之类的类。我们如何使用FIPS BouncyCastle做同样的事情？

Answer 1

我发现了以下对我有用的解决方案：

public static PublicKey getPublicKeyForPrivateKeyEC(ECPrivateKey privateKey) throws GeneralSecurityException {
    final KeyFactory keyFactory = KeyFactory.getInstance("ECDSA", new BouncyCastleProvider());
    final ECParameterSpec ecSpec = privateKey.getParams();
    final ECCurve ecCurve = FipsECUtil.convertCurve(ecSpec);
    final ECMultiplier multiplier = ecCurve.getMultiplier();
    final ECPoint generatorP = FipsECUtil.convertPoint(ecSpec, ecSpec.getGenerator());
    final ECPoint q = multiplier.multiply(generatorP, privateKey.getS());
    final byte[] publicDerBytes = q.getEncoded(false);
    final ECPoint point = ecCurve.decodePoint(publicDerBytes);
    final ECPublicKeySpec pubSpec = new ECPublicKeySpec(new java.security.spec.ECPoint(
        point.getAffineXCoord().toBigInteger(), 
        point.getAffineYCoord().toBigInteger()), ecSpec);
    return keyFactory.generatePublic(pubSpec);
}