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Assets/BestHTTP/SecureProtocol/crypto/engines/ChaCha7539Engine.cs

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+#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
+using System;
+
+using Org.BouncyCastle.Crypto.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Engines
+{
+    /// <summary>
+    /// Implementation of Daniel J. Bernstein's ChaCha stream cipher.
+    /// </summary>
+    public class ChaCha7539Engine
+        : Salsa20Engine
+    {
+        /// <summary>
+        /// Creates a 20 rounds ChaCha engine.
+        /// </summary>
+        public ChaCha7539Engine()
+        {
+        }
+
+        public override string AlgorithmName
+        {
+            get { return "ChaCha" + rounds; }
+        }
+
+        protected override int NonceSize
+        {
+            get { return 12; }
+        }
+
+        protected override void AdvanceCounter()
+        {
+            if (++engineState[12] == 0)
+                throw new InvalidOperationException("attempt to increase counter past 2^32.");
+        }
+
+        protected override void ResetCounter()
+        {
+            engineState[12] = 0;
+        }
+
+        protected override void SetKey(byte[] keyBytes, byte[] ivBytes)
+        {
+            if (keyBytes != null)
+            {
+                if (keyBytes.Length != 32)
+                    throw new ArgumentException(AlgorithmName + " requires 256 bit key");
+
+                PackTauOrSigma(keyBytes.Length, engineState, 0);
+
+                // Key
+                Pack.LE_To_UInt32(keyBytes, 0, engineState, 4, 8);
+            }
+
+            // IV
+            Pack.LE_To_UInt32(ivBytes, 0, engineState, 13, 3);
+        }
+
+        protected override void GenerateKeyStream(byte[] output)
+        {
+            ChaChaEngine.ChachaCore(rounds, engineState, x);
+            Pack.UInt32_To_LE(x, output, 0);
+        }
+    }
+}
+#endif