diff --git a/shadowsocks-csharp/Controller/Service/UpdateChecker.cs b/shadowsocks-csharp/Controller/Service/UpdateChecker.cs
index 6ae51eaf..64d223b0 100644
--- a/shadowsocks-csharp/Controller/Service/UpdateChecker.cs
+++ b/shadowsocks-csharp/Controller/Service/UpdateChecker.cs
@@ -41,6 +41,7 @@ namespace Shadowsocks.Controller
         {
 #if DEBUG
             return;
+#pragma warning disable CS0162 // 检测到无法访问的代码
 #endif
             CheckUpdateTimer timer = new CheckUpdateTimer(delay);
             timer.AutoReset = false;
diff --git a/shadowsocks-csharp/Encryption/AEAD/AEADAesGcmNativeEncryptor.cs b/shadowsocks-csharp/Encryption/AEAD/AEADAesGcmNativeEncryptor.cs
index 363da9db..788f3544 100644
--- a/shadowsocks-csharp/Encryption/AEAD/AEADAesGcmNativeEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/AEAD/AEADAesGcmNativeEncryptor.cs
@@ -29,19 +29,19 @@ namespace Shadowsocks.Encryption.AEAD
         }
         #endregion
 
-        public override int CipherEncrypt(Span<byte> plain, Span<byte> cipher)
+        public override int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
         {
             using AesGcm aes = new AesGcm(sessionKey);
             aes.Encrypt(nonce.AsSpan(), plain, cipher.Slice(0, plain.Length), cipher.Slice(plain.Length, tagLen));
             return plain.Length + tagLen;
         }
 
-        public override int CipherDecrypt(Span<byte> plain, Span<byte> cipher)
+        public override int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
         {
             int clen = cipher.Length - tagLen;
             using AesGcm aes = new AesGcm(sessionKey);
-            Span<byte> ciphertxt = cipher.Slice(0, clen);
-            Span<byte> tag = cipher.Slice(clen);
+            ReadOnlySpan<byte> ciphertxt = cipher.Slice(0, clen);
+            ReadOnlySpan<byte> tag = cipher.Slice(clen);
             aes.Decrypt(nonce.AsSpan(), ciphertxt, tag, plain.Slice(0, clen));
             return clen;
         }
diff --git a/shadowsocks-csharp/Encryption/AEAD/AEADEncryptor.cs b/shadowsocks-csharp/Encryption/AEAD/AEADEncryptor.cs
index 1a2151cf..29a18ceb 100644
--- a/shadowsocks-csharp/Encryption/AEAD/AEADEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/AEAD/AEADEncryptor.cs
@@ -104,8 +104,8 @@ namespace Shadowsocks.Encryption.AEAD
             DeriveSessionKey(salt, masterKey, sessionKey);
         }
 
-        public abstract int CipherEncrypt(Span<byte> plain, Span<byte> cipher);
-        public abstract int CipherDecrypt(Span<byte> plain, Span<byte> cipher);
+        public abstract int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher);
+        public abstract int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher);
 
         #region TCP
 
@@ -328,7 +328,7 @@ namespace Shadowsocks.Encryption.AEAD
 
         #endregion
 
-        private int ChunkEncrypt(Span<byte> plain, Span<byte> cipher)
+        private int ChunkEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
         {
             if (plain.Length > ChunkLengthMask)
             {
@@ -344,5 +344,25 @@ namespace Shadowsocks.Encryption.AEAD
 
             return cipherLenSize + cipherDataSize;
         }
+
+        public override int Encrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override int Decrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override int EncryptUDP(ReadOnlySpan<byte> plain, Span<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override int DecryptUDP(Span<byte> plain, ReadOnlySpan<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
     }
 }
\ No newline at end of file
diff --git a/shadowsocks-csharp/Encryption/AEAD/AEADNaClEncryptor.cs b/shadowsocks-csharp/Encryption/AEAD/AEADNaClEncryptor.cs
index d7579af6..0fb2ff55 100644
--- a/shadowsocks-csharp/Encryption/AEAD/AEADNaClEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/AEAD/AEADNaClEncryptor.cs
@@ -46,14 +46,14 @@ namespace Shadowsocks.Encryption.AEAD
             }
         }
 
-        public override int CipherEncrypt(Span<byte> plain, Span<byte> cipher)
+        public override int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
         {
             byte[] ct = enc.Encrypt(plain, null, nonce);
             ct.CopyTo(cipher);
             return ct.Length;
         }
 
-        public override int CipherDecrypt(Span<byte> plain, Span<byte> cipher)
+        public override int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
         {
             byte[] pt = enc.Decrypt(cipher, null, nonce);
             pt.CopyTo(plain);
diff --git a/shadowsocks-csharp/Encryption/EncryptorBase.cs b/shadowsocks-csharp/Encryption/EncryptorBase.cs
index bd29137f..32d79847 100644
--- a/shadowsocks-csharp/Encryption/EncryptorBase.cs
+++ b/shadowsocks-csharp/Encryption/EncryptorBase.cs
@@ -1,4 +1,6 @@
-namespace Shadowsocks.Encryption
+using System;
+
+namespace Shadowsocks.Encryption
 {
     public abstract class EncryptorBase : IEncryptor
     {
@@ -44,6 +46,11 @@
             return $"{instanceId}({Method},{Password})";
         }
 
+        public abstract int Encrypt(ReadOnlySpan<byte> plain, Span<byte> cipher);
+        public abstract int Decrypt(Span<byte> plain, ReadOnlySpan<byte> cipher);
+        public abstract int EncryptUDP(ReadOnlySpan<byte> plain, Span<byte> cipher);
+        public abstract int DecryptUDP(Span<byte> plain, ReadOnlySpan<byte> cipher);
+
         public int AddressBufferLength { get; set; } = -1;
     }
 }
\ No newline at end of file
diff --git a/shadowsocks-csharp/Encryption/IEncryptor.cs b/shadowsocks-csharp/Encryption/IEncryptor.cs
index 00600a21..76efa1bf 100644
--- a/shadowsocks-csharp/Encryption/IEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/IEncryptor.cs
@@ -11,5 +11,9 @@ namespace Shadowsocks.Encryption
         void Decrypt(byte[] buf, int length, byte[] outbuf, out int outlength);
         void EncryptUDP(byte[] buf, int length, byte[] outbuf, out int outlength);
         void DecryptUDP(byte[] buf, int length, byte[] outbuf, out int outlength);
+        int Encrypt(ReadOnlySpan<byte> plain, Span<byte> cipher);
+        int Decrypt(Span<byte> plain, ReadOnlySpan<byte> cipher);
+        int EncryptUDP(ReadOnlySpan<byte> plain, Span<byte> cipher);
+        int DecryptUDP(Span<byte> plain, ReadOnlySpan<byte> cipher);
     }
 }
diff --git a/shadowsocks-csharp/Encryption/Stream/StreamAesBouncyCastleEncryptor.cs b/shadowsocks-csharp/Encryption/Stream/StreamAesBouncyCastleEncryptor.cs
index b602b045..6a6ea32b 100644
--- a/shadowsocks-csharp/Encryption/Stream/StreamAesBouncyCastleEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/Stream/StreamAesBouncyCastleEncryptor.cs
@@ -23,19 +23,19 @@ namespace Shadowsocks.Encryption.Stream
             b.Init(isEncrypt, new ParametersWithIV(new KeyParameter(key), iv));
         }
 
-        protected override int CipherEncrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
         {
             CipherUpdate(plain, cipher);
             return plain.Length;
         }
 
-        protected override int CipherDecrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
         {
             CipherUpdate(cipher, plain);
             return cipher.Length;
         }
 
-        private void CipherUpdate(Span<byte> i, Span<byte> o)
+        private void CipherUpdate(ReadOnlySpan<byte> i, Span<byte> o)
         {
             Span<byte> ob = new byte[o.Length + 128];
             i.CopyTo(cfbBuf.AsSpan(ptr));
diff --git a/shadowsocks-csharp/Encryption/Stream/StreamChachaNaClEncryptor.cs b/shadowsocks-csharp/Encryption/Stream/StreamChachaNaClEncryptor.cs
index 8fd3512d..e8670109 100644
--- a/shadowsocks-csharp/Encryption/Stream/StreamChachaNaClEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/Stream/StreamChachaNaClEncryptor.cs
@@ -24,17 +24,17 @@ namespace Shadowsocks.Encryption.Stream
         {
         }
 
-        protected override int CipherDecrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
         {
             return CipherUpdate(cipher, plain, false);
         }
 
-        protected override int CipherEncrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
         {
             return CipherUpdate(plain, cipher, true);
         }
 
-        private int CipherUpdate(Span<byte> i, Span<byte> o, bool enc)
+        private int CipherUpdate(ReadOnlySpan<byte> i, Span<byte> o, bool enc)
         {
             int len = i.Length;
             int pad = remain;
diff --git a/shadowsocks-csharp/Encryption/Stream/StreamEncryptor.cs b/shadowsocks-csharp/Encryption/Stream/StreamEncryptor.cs
index 604be0ca..4d1c97e6 100644
--- a/shadowsocks-csharp/Encryption/Stream/StreamEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/Stream/StreamEncryptor.cs
@@ -85,8 +85,8 @@ namespace Shadowsocks.Encryption.Stream
             Array.Copy(iv, this.iv, ivLen);
         }
 
-        protected abstract int CipherEncrypt(Span<byte> plain, Span<byte> cipher);
-        protected abstract int CipherDecrypt(Span<byte> plain, Span<byte> cipher);
+        protected abstract int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher);
+        protected abstract int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher);
 
         #region TCP
         [MethodImpl(MethodImplOptions.Synchronized)]
@@ -193,5 +193,25 @@ namespace Shadowsocks.Encryption.Stream
         }
 
         #endregion
+
+        public override int Encrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override int Decrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override int EncryptUDP(ReadOnlySpan<byte> plain, Span<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
+
+        public override int DecryptUDP(Span<byte> plain, ReadOnlySpan<byte> cipher)
+        {
+            throw new NotImplementedException();
+        }
     }
 }
\ No newline at end of file
diff --git a/shadowsocks-csharp/Encryption/Stream/StreamPlainNativeEncryptor.cs b/shadowsocks-csharp/Encryption/Stream/StreamPlainNativeEncryptor.cs
index d560b4bb..33a59dcc 100644
--- a/shadowsocks-csharp/Encryption/Stream/StreamPlainNativeEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/Stream/StreamPlainNativeEncryptor.cs
@@ -10,13 +10,13 @@ namespace Shadowsocks.Encryption.Stream
         {
         }
 
-        protected override int CipherDecrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
         {
             cipher.CopyTo(plain);
             return cipher.Length;
         }
 
-        protected override int CipherEncrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
         {
             plain.CopyTo(cipher);
             return plain.Length;
diff --git a/shadowsocks-csharp/Encryption/Stream/StreamRc4NativeEncryptor.cs b/shadowsocks-csharp/Encryption/Stream/StreamRc4NativeEncryptor.cs
index f8776954..367b8080 100644
--- a/shadowsocks-csharp/Encryption/Stream/StreamRc4NativeEncryptor.cs
+++ b/shadowsocks-csharp/Encryption/Stream/StreamRc4NativeEncryptor.cs
@@ -29,17 +29,17 @@ namespace Shadowsocks.Encryption.Stream
             sbox = SBox(realkey);
         }
 
-        protected override int CipherEncrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherEncrypt(ReadOnlySpan<byte> plain, Span<byte> cipher)
         {
             return CipherUpdate(plain, cipher);
         }
 
-        protected override int CipherDecrypt(Span<byte> plain, Span<byte> cipher)
+        protected override int CipherDecrypt(Span<byte> plain, ReadOnlySpan<byte> cipher)
         {
             return CipherUpdate(cipher, plain);
         }
 
-        private int CipherUpdate(Span<byte> i, Span<byte> o)
+        private int CipherUpdate(ReadOnlySpan<byte> i, Span<byte> o)
         {
             // don't know why we need third array, but it works...
             Span<byte> t = new byte[i.Length];