c# - 在 Bouncy CaSTLe C# 中从私钥获取公钥

Question

所以我有一个加密的私钥 PEM。我可以阅读它并通过以下方式获取私钥:

AsymmetricKeyParameter key;
using (var sr = new StringReader(pem))
using (var pf = new PassowrdFinder { Password = password })
{
  var reader = new PemReader(sr, pf);
  key = (AsymmetricKeyParameter)reader.ReadObject();
}

我还需要公钥，以便稍后创建 SPKI。我试过了

var keyPair = new AsymmetricCipherKeyPair(key, key);

失败并显示 System.ArgumentException: Expected a public key Parameter name: publicParameter。

我的问题是:如何从私钥中获取公钥？

Answer 1

感谢 James K Polk 的帮助，这是我的想法

    AsymmetricCipherKeyPair GetKeyPairFromPrivateKey(AsymmetricKeyParameter privateKey)
    {
        AsymmetricCipherKeyPair keyPair = null;
        if (privateKey is RsaPrivateCrtKeyParameters rsa)
        {
            var pub = new RsaKeyParameters(false, rsa.Modulus, rsa.PublicExponent);
            keyPair = new AsymmetricCipherKeyPair(pub, privateKey);
        }
        else if (privateKey is Ed25519PrivateKeyParameters ed)
        {
            var pub = ed.GeneratePublicKey();
            keyPair = new AsymmetricCipherKeyPair(pub, privateKey);
        }
        else if (privateKey is ECPrivateKeyParameters ec)
        {
            var q = ec.Parameters.G.Multiply(ec.D);
            var pub = new ECPublicKeyParameters(ec.AlgorithmName, q, ec.PublicKeyParamSet);
            keyPair = new AsymmetricCipherKeyPair(pub, ec);
        }
        if (keyPair == null)
            throw new NotSupportedException($"The key type {privateKey.GetType().Name} is not supported.");

        return keyPair;
    }