init commit

output/Libraries/BouncyCastle.Crypto/Org/BouncyCastle/Crypto/Engines/RC4Engine.cs

@@ -0,0 +1,86 @@
+using System;
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Crypto.Engines;
+
+public class RC4Engine : IStreamCipher
+{
+	private static readonly int STATE_LENGTH = 256;
+
+	private byte[] engineState;
+
+	private int x;
+
+	private int y;
+
+	private byte[] workingKey;
+
+	public virtual string AlgorithmName => "RC4";
+
+	public virtual void Init(bool forEncryption, ICipherParameters parameters)
+	{
+		if (parameters is KeyParameter)
+		{
+			workingKey = ((KeyParameter)parameters).GetKey();
+			SetKey(workingKey);
+			return;
+		}
+		throw new ArgumentException("invalid parameter passed to RC4 init - " + Platform.GetTypeName(parameters));
+	}
+
+	public virtual byte ReturnByte(byte input)
+	{
+		x = (x + 1) & 0xFF;
+		y = (engineState[x] + y) & 0xFF;
+		byte b = engineState[x];
+		engineState[x] = engineState[y];
+		engineState[y] = b;
+		return (byte)(input ^ engineState[(engineState[x] + engineState[y]) & 0xFF]);
+	}
+
+	public virtual void ProcessBytes(byte[] input, int inOff, int length, byte[] output, int outOff)
+	{
+		Check.DataLength(input, inOff, length, "input buffer too short");
+		Check.OutputLength(output, outOff, length, "output buffer too short");
+		for (int i = 0; i < length; i++)
+		{
+			x = (x + 1) & 0xFF;
+			y = (engineState[x] + y) & 0xFF;
+			byte b = engineState[x];
+			engineState[x] = engineState[y];
+			engineState[y] = b;
+			output[i + outOff] = (byte)(input[i + inOff] ^ engineState[(engineState[x] + engineState[y]) & 0xFF]);
+		}
+	}
+
+	public virtual void Reset()
+	{
+		SetKey(workingKey);
+	}
+
+	private void SetKey(byte[] keyBytes)
+	{
+		workingKey = keyBytes;
+		x = 0;
+		y = 0;
+		if (engineState == null)
+		{
+			engineState = new byte[STATE_LENGTH];
+		}
+		for (int i = 0; i < STATE_LENGTH; i++)
+		{
+			engineState[i] = (byte)i;
+		}
+		int num = 0;
+		int num2 = 0;
+		for (int j = 0; j < STATE_LENGTH; j++)
+		{
+			num2 = ((keyBytes[num] & 0xFF) + engineState[j] + num2) & 0xFF;
+			byte b = engineState[j];
+			engineState[j] = engineState[num2];
+			engineState[num2] = b;
+			num = (num + 1) % keyBytes.Length;
+		}
+	}
+}