dlech.SshAgentLib.PpkFormatter.CreateCipherKeyPair C# (CSharp) Method

        private static AsymmetricCipherKeyPair CreateCipherKeyPair(
      PublicKeyAlgorithm algorithm,
      byte[] publicKeyBlob, byte[] privateKeyBlob)
        {
            var parser = new BlobParser(publicKeyBlob);
              var publicKey = parser.ReadSsh2PublicKeyData();
              parser = new BlobParser(privateKeyBlob);

              switch (algorithm) {
            case PublicKeyAlgorithm.SSH_RSA:
              var rsaPublicKeyParams = (RsaKeyParameters)publicKey;

              var d = new BigInteger(1, parser.ReadBlob());
              var p = new BigInteger(1, parser.ReadBlob());
              var q = new BigInteger(1, parser.ReadBlob());
              var inverseQ = new BigInteger(1, parser.ReadBlob());

              /* compute missing parameters */
              var dp = d.Remainder(p.Subtract(BigInteger.One));
              var dq = d.Remainder(q.Subtract(BigInteger.One));

              RsaPrivateCrtKeyParameters rsaPrivateKeyParams =
            new RsaPrivateCrtKeyParameters(rsaPublicKeyParams.Modulus,
              rsaPublicKeyParams.Exponent, d, p, q, dp, dq, inverseQ);

              return new AsymmetricCipherKeyPair(rsaPublicKeyParams,
            rsaPrivateKeyParams);

            case PublicKeyAlgorithm.SSH_DSS:
              var dsaPublicKeyParams = (DsaPublicKeyParameters)publicKey;

              var x = new BigInteger(1, parser.ReadBlob());
              DsaPrivateKeyParameters dsaPrivateKeyParams =
            new DsaPrivateKeyParameters(x, dsaPublicKeyParams.Parameters);

              return new AsymmetricCipherKeyPair(dsaPublicKeyParams,
            dsaPrivateKeyParams);
            case PublicKeyAlgorithm.ED25519:
              var ed25596PublicKey = (Ed25519PublicKeyParameter)publicKey;

              byte[] privBlob = parser.ReadBlob();
              byte[] privSig = new byte[64];
              // OpenSSH's "private key" is actually the private key with the public key tacked on ...
              Array.Copy(privBlob, 0, privSig, 0, 32);
              Array.Copy(ed25596PublicKey.Key, 0, privSig, 32, 32);
              var ed25596PrivateKey = new Ed25519PrivateKeyParameter(privSig);

              return new AsymmetricCipherKeyPair(ed25596PublicKey, ed25596PrivateKey);
            case PublicKeyAlgorithm.ECDSA_SHA2_NISTP256:
            case PublicKeyAlgorithm.ECDSA_SHA2_NISTP384:
            case PublicKeyAlgorithm.ECDSA_SHA2_NISTP521:
              var ecPublicKeyParams = (ECPublicKeyParameters)publicKey;

              var ecdsaPrivate = new BigInteger(1, parser.ReadBlob());
              ECPrivateKeyParameters ecPrivateKeyParams =
            new ECPrivateKeyParameters(ecdsaPrivate, ecPublicKeyParams.Parameters);

              return new AsymmetricCipherKeyPair(ecPublicKeyParams, ecPrivateKeyParams);
            default:
              // unsupported encryption algorithm
              throw new PpkFormatterException(PpkFormatterException.PpkErrorType.PublicKeyEncryption);
              }
        }