Some refactor

Author: scott-xu

src/Renci.SshNet/Security/KeyExchangeECCurve25519.cs

@@ -6,11 +6,13 @@ namespace Renci.SshNet.Security
 {
     internal partial class KeyExchangeECCurve25519 : KeyExchangeEC
     {
+#pragma warning disable SA1401 // Fields should be private
 #if NET
-        private Impl _impl;
+        protected Impl _impl;
 #else
-        private BouncyCastleImpl _impl;
+        protected BouncyCastleImpl _impl;
 #endif
+#pragma warning restore SA1401 // Fields should be private
 
         /// <summary>
         /// Gets algorithm name.
@@ -35,17 +37,6 @@ protected override int HashSize
         public override void Start(Session session, KeyExchangeInitMessage message, bool sendClientInitMessage)
         {
             base.Start(session, message, sendClientInitMessage);
-            StartImpl();
-        }
-
-        /// <summary>
-        /// The implementation of start key exchange algorithm.
-        /// </summary>
-        protected virtual void StartImpl()
-        {
-            Session.RegisterMessage("SSH_MSG_KEX_ECDH_REPLY");
-
-            Session.KeyExchangeEcdhReplyMessageReceived += Session_KeyExchangeEcdhReplyMessageReceived;
 #if NET
             if (System.OperatingSystem.IsWindowsVersionAtLeast(10))
             {
@@ -58,6 +49,18 @@ protected virtual void StartImpl()
                 _impl = new BouncyCastleImpl();
             }
 
+            StartImpl();
+        }
+
+        /// <summary>
+        /// The implementation of start key exchange algorithm.
+        /// </summary>
+        protected virtual void StartImpl()
+        {
+            Session.RegisterMessage("SSH_MSG_KEX_ECDH_REPLY");
+
+            Session.KeyExchangeEcdhReplyMessageReceived += Session_KeyExchangeEcdhReplyMessageReceived;
+
             _clientExchangeValue = _impl.GenerateClientECPoint();
 
             SendMessage(new KeyExchangeEcdhInitMessage(_clientExchangeValue));

src/Renci.SshNet/Security/KeyExchangeECDH.BouncyCastleImpl.cs

@@ -12,12 +12,12 @@ internal abstract partial class KeyExchangeECDH
         private sealed class BouncyCastleImpl : Impl
         {
             private readonly ECDomainParameters _domainParameters;
-            private readonly ECDHCBasicAgreement _keyAgreement;
+            private readonly ECDHBasicAgreement _keyAgreement;
 
             public BouncyCastleImpl(X9ECParameters curveParameters)
             {
                 _domainParameters = new ECDomainParameters(curveParameters);
-                _keyAgreement = new ECDHCBasicAgreement();
+                _keyAgreement = new ECDHBasicAgreement();
             }
 
             public override byte[] GenerateClientECPoint()

src/Renci.SshNet/Security/KeyExchangeMLKem768X25519Sha256.cs

@@ -14,11 +14,6 @@ namespace Renci.SshNet.Security
     internal sealed class KeyExchangeMLKem768X25519Sha256 : KeyExchangeECCurve25519
     {
         private MLKemDecapsulator _mlkemDecapsulator;
-#if NET
-        private Impl _impl;
-#else
-        private BouncyCastleImpl _impl;
-#endif
 
         /// <summary>
         /// Gets algorithm name.
@@ -54,17 +49,6 @@ protected override void StartImpl()
             _mlkemDecapsulator.Init(mlkem768KeyPair.Private);
 
             var mlkem768PublicKey = ((MLKemPublicKeyParameters)mlkem768KeyPair.Public).GetEncoded();
-#if NET
-            if (System.OperatingSystem.IsWindowsVersionAtLeast(10))
-            {
-                var curve = System.Security.Cryptography.ECCurve.CreateFromFriendlyName("Curve25519");
-                _impl = new BclImpl(curve);
-            }
-            else
-#endif
-            {
-                _impl = new BouncyCastleImpl();
-            }
 
             var x25519PublicKey = _impl.GenerateClientECPoint();
 
@@ -131,16 +115,5 @@ private void HandleServerHybridReply(byte[] hostKey, byte[] serverExchangeValue,
 
             SharedKey = CryptoAbstraction.HashSHA256(mlkemSecret.Concat(x25519Agreement));
         }
-
-        /// <inheritdoc/>
-        protected override void Dispose(bool disposing)
-        {
-            base.Dispose(disposing);
-
-            if (disposing)
-            {
-                _impl?.Dispose();
-            }
-        }
     }
 }

src/Renci.SshNet/Security/KeyExchangeSNtruP761X25519Sha512.cs

@@ -13,11 +13,6 @@ namespace Renci.SshNet.Security
     internal sealed class KeyExchangeSNtruP761X25519Sha512 : KeyExchangeECCurve25519
     {
         private SNtruPrimeKemExtractor _sntrup761Extractor;
-#if NET
-        private Impl _impl;
-#else
-        private BouncyCastleImpl _impl;
-#endif
 
         /// <summary>
         /// Gets algorithm name.
@@ -52,24 +47,11 @@ protected override void StartImpl()
             _sntrup761Extractor = new SNtruPrimeKemExtractor((SNtruPrimePrivateKeyParameters)sntrup761KeyPair.Private);
 
             var sntrup761PublicKey = ((SNtruPrimePublicKeyParameters)sntrup761KeyPair.Public).GetEncoded();
-#if NET
-            if (System.OperatingSystem.IsWindowsVersionAtLeast(10))
-            {
-                var curve = System.Security.Cryptography.ECCurve.CreateFromFriendlyName("Curve25519");
-                _impl = new BclImpl(curve);
-            }
-            else
-#endif
-            {
-                _impl = new BouncyCastleImpl();
-            }
 
             var x25519PublicKey = _impl.GenerateClientECPoint();
 
             _clientExchangeValue = sntrup761PublicKey.Concat(x25519PublicKey);
 
-            _clientExchangeValue = sntrup761PublicKey.Concat(x25519PublicKey);
-
             SendMessage(new KeyExchangeEcdhInitMessage(_clientExchangeValue));
         }
 
@@ -131,16 +113,5 @@ private void HandleServerEcdhReply(byte[] hostKey, byte[] serverExchangeValue, b
 
             SharedKey = CryptoAbstraction.HashSHA512(sntrup761Secret.Concat(x25519Agreement));
         }
-
-        /// <inheritdoc/>
-        protected override void Dispose(bool disposing)
-        {
-            base.Dispose(disposing);
-
-            if (disposing)
-            {
-                _impl?.Dispose();
-            }
-        }
     }
 }