Optimise encryption, avoid creating multiple transformer per transform

Kaioru · Oct 10, 2023 · 577def4 · 577def4
1 parent f7f7c32
commit 577def4
Showing 1 changed file with 8 additions and 9 deletions.
diff --git a/src/common/Edelstein.Common.Crypto/AESCipher.cs b/src/common/Edelstein.Common.Crypto/AESCipher.cs
@@ -4,7 +4,7 @@ namespace Edelstein.Common.Crypto;
 
 public class AESCipher
 {
-    private readonly SymmetricAlgorithm _cipher;
+    private readonly ICryptoTransform _transformer;
 
     public AESCipher() : this(new byte[] { 0x13, 0x08, 0x06, 0xb4, 0x1b, 0x0f, 0x33, 0x52 })
     {
@@ -13,14 +13,15 @@ public AESCipher() : this(new byte[] { 0x13, 0x08, 0x06, 0xb4, 0x1b, 0x0f, 0x33,
     public AESCipher(ReadOnlySpan<byte> userKey)
     {
         var expandedKey = new byte[userKey.Length * 4];
+        var cipher = Aes.Create();
 
         for (var i = 0; i < userKey.Length; i++)
             expandedKey[i * 4] = userKey[i];
-
-        _cipher = Aes.Create();
-        _cipher.KeySize = 256;
-        _cipher.Key = expandedKey;
-        _cipher.Mode = CipherMode.ECB;
+        
+        cipher.KeySize = 256;
+        cipher.Key = expandedKey;
+        cipher.Mode = CipherMode.ECB;
+        _transformer = cipher.CreateEncryptor();
     }
 
     public void Transform(Span<byte> input, uint pSrc)
@@ -32,8 +33,6 @@ public void Transform(Span<byte> input, uint pSrc)
         var srcExp = new byte[sizeof(int) * 4];
         var srcBytes = BitConverter.GetBytes(pSrc);
 
-        using var crypt = _cipher.CreateEncryptor();
-
         while (remaining > 0)
         {
             for (var i = 0; i < srcExp.Length; ++i)
@@ -48,7 +47,7 @@ public void Transform(Span<byte> input, uint pSrc)
 
                 if (sub % srcExp.Length == 0)
                 {
-                    var result = crypt.TransformFinalBlock(srcExp, 0, srcExp.Length);
+                    var result = _transformer.TransformFinalBlock(srcExp, 0, srcExp.Length);
                     Array.Copy(result, srcExp, srcExp.Length);
                 }