如果知道曲线名称，如何构造PrivateKey原始私钥/点

Question

要求:对于给定的命名曲线，发送尽可能少的数据，以便接收方可以构造EC PrivateKey

我目前在Android上使用BouncyCastle/海绵城堡。这是我到目前为止所理解的。

KeyPairGenerator keyGen = KeyPairGenerator.getInstance("EC");
ECGenParameterSpec ecGenParameterSpec = new ECGenParameterSpec("secp112r2");
keyGen.initialize(ecGenParameterSpec, new SecureRandom());
KeyPair keyPair = keyGen.generateKeyPair();
PrivateKey privateKey = keyPair.getPrivate();
// privateKey.getEncoded() -> gives DER encoded private key. I can construct PrivateKey from that easily
byte[] derEncodedPrivateKeyBytes = privateKey.getEncoded(); // byteArray length-> 80
KeyFactory kf = KeyFactory.getInstance("EC");
PrivateKey key = kf.generatePrivate(new PKCS8EncodedKeySpec(derEncodedPrivateKeyBytes));

现在，使用Bouncy/sponge城堡，我得到了私钥的实际点，而没有derEncoding中存在的任何其他信息。

ECPrivateKeyParameters param = (ECPrivateKeyParameters) ECUtil.generatePrivateKeyParameter(privateKey);
int lenghtOfKey = param.getD().toByteArray().length; // length - 14

问题:如何通过点D (privateKeyParam.getD())和曲线名称来重建PrivateKey对象?使用曲线名称，我可以得到ECCurveParameters.

编辑:我能够使用私钥点(praram.getD())构建ECPrivateKeyParameters，但仍然无法弄清楚如何从ECPrivateKeyParameters生成PrivateKey。

X9ECParameters ecCurve = ECNamedCurveTable.getByName(curveName);
ECDomainParameters ecDomainParam = new ECDomainParameters(ecCurve.getCurve(),
        ecCurve.getG(), ecCurve.getN(), ecCurve.getH(), ecCurve.getSeed());
ECPrivateKeyParameters generatedECPrivateKeyParams = new ECPrivateKeyParameters(param.getD(), ecDomainParam);

Answer 1

我能够弄清楚如何从BigInteger D &曲线的名字。

 public static PrivateKey getPrivateKeyFromECBigIntAndCurve(BigInteger s, String curveName) {
    X9ECParameters ecCurve = ECNamedCurveTable.getByName(curveName);
    ECParameterSpec ecParameterSpec = new ECNamedCurveSpec(curveName, ecCurve.getCurve(), ecCurve.getG(), ecCurve.getN(), ecCurve.getH(), ecCurve.getSeed());
    ECPrivateKeySpec privateKeySpec = new ECPrivateKeySpec(s, ecParameterSpec);
    try {
        KeyFactory keyFactory = KeyFactory.getInstance("EC");
        return keyFactory.generatePrivate(privateKeySpec);
    } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
        e.printStackTrace();
        return null;
    }
}