Granados.SSH2.SSH2UserAuthKey.WritePrivatePartInSECSHStyleFile C# (CSharp) Method

        public void WritePrivatePartInSECSHStyleFile(Stream dest, string comment, string passphrase)
        {
            //step1 key body
            SSH2DataWriter wr = new SSH2DataWriter();
            wr.WriteInt32(0); //this field is filled later
            if (_keypair.Algorithm == PublicKeyAlgorithm.RSA) {
                RSAKeyPair rsa = (RSAKeyPair)_keypair;
                RSAPublicKey pub = (RSAPublicKey)_keypair.PublicKey;
                wr.WriteBigIntWithBits(pub.Exponent);
                wr.WriteBigIntWithBits(rsa.D);
                wr.WriteBigIntWithBits(pub.Modulus);
                wr.WriteBigIntWithBits(rsa.U);
                wr.WriteBigIntWithBits(rsa.P);
                wr.WriteBigIntWithBits(rsa.Q);
            }
            else {
                DSAKeyPair dsa = (DSAKeyPair)_keypair;
                DSAPublicKey pub = (DSAPublicKey)_keypair.PublicKey;
                wr.WriteInt32(0);
                wr.WriteBigIntWithBits(pub.P);
                wr.WriteBigIntWithBits(pub.G);
                wr.WriteBigIntWithBits(pub.Q);
                wr.WriteBigIntWithBits(pub.Y);
                wr.WriteBigIntWithBits(dsa.X);
            }

            int padding_len = 0;
            if (passphrase != null) {
                padding_len = 8 - (int)wr.Length % 8;
                wr.Write(new byte[padding_len]);
            }
            byte[] encrypted_body = wr.ToByteArray();
            SSHUtil.WriteIntToByteArray(encrypted_body, 0, encrypted_body.Length - padding_len - 4);

            //encrypt if necessary
            if (passphrase != null) {
                Cipher c = CipherFactory.CreateCipher(SSHProtocol.SSH2, CipherAlgorithm.TripleDES, PassphraseToKey(passphrase, 24));
                Debug.Assert(encrypted_body.Length % 8 == 0);
                byte[] tmp = new Byte[encrypted_body.Length];
                c.Encrypt(encrypted_body, 0, encrypted_body.Length, tmp, 0);
                encrypted_body = tmp;
            }

            //step2 make binary key data
            wr = new SSH2DataWriter();
            wr.WriteInt32(MAGIC_VAL);
            wr.WriteInt32(0); //for total size
            wr.WriteString(_keypair.Algorithm == PublicKeyAlgorithm.RSA ?
                "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}" :
                "dl-modp{sign{dsa-nist-sha1},dh{plain}}");

            wr.WriteString(passphrase == null ? "none" : "3des-cbc");
            wr.WriteAsString(encrypted_body);

            byte[] rawdata = wr.ToByteArray();
            SSHUtil.WriteIntToByteArray(rawdata, 4, rawdata.Length); //fix total length

            //step3 write final data
            StreamWriter sw = new StreamWriter(dest, Encoding.ASCII);
            sw.WriteLine("---- BEGIN SSH2 ENCRYPTED PRIVATE KEY ----");
            if (comment != null)
                WriteKeyFileBlock(sw, "Comment: " + comment, true);
            WriteKeyFileBlock(sw, Encoding.ASCII.GetString(Base64.Encode(rawdata)), false);
            sw.WriteLine("---- END SSH2 ENCRYPTED PRIVATE KEY ----");
            sw.Close();
        }

        //Tutorial: Generating a new RSA key for user authentication
        private static void GenerateRSAKey() {
            //RSA KEY GENERATION TEST
            byte[] testdata = Encoding.ASCII.GetBytes("CHRISTIAN VIERI");
            RSAKeyPair kp = RSAKeyPair.GenerateNew(2048, new Random());

            //sign and verify test
            byte[] sig = kp.Sign(testdata);
            kp.Verify(sig, testdata);

            //export / import test
            SSH2UserAuthKey key = new SSH2UserAuthKey(kp);
            key.WritePublicPartInOpenSSHStyle(new FileStream("newrsakey.pub", FileMode.Create));
            key.WritePrivatePartInSECSHStyleFile(new FileStream("newrsakey.bin", FileMode.Create), "comment", "passphrase");
            //read test
            SSH2UserAuthKey newpk = SSH2UserAuthKey.FromSECSHStyleFile("newrsakey.bin", "passphrase");
        }