public static void InitRC4Encryption(byte[] secretKey, byte[] pubKeyIn, byte[] pubKeyOut, RC4_KEY rc4keyIn,
RC4_KEY rc4keyOut)
{
var sha256 = new HMACSHA256(secretKey);
var digest = sha256.TransformFinalBlock(pubKeyIn, 0, pubKeyIn.Length);
Prepare_key(rc4keyOut, digest, 16);
digest = sha256.TransformFinalBlock(pubKeyOut, 0, pubKeyOut.Length);
Prepare_key(rc4keyIn, digest, 16);
}
public static void RC4(BufferWithOffset buffer, RC4_KEY key, long length)
{
var state = new byte[256];
short counter;
byte x = key.x;
byte y = key.y;
Buffer.BlockCopy(key.data, 0, state, 0, 256);
for (counter = 0; counter < length; counter++)
{
x = (byte)((x + 1) % 256);
y = (byte)((state[x] + y) % 256);
var temp = state[x];
state[x] = state[y];
state[y] = temp;
var xorIndex = (byte)((state[x] + state[y]) % 256);
buffer[counter] ^= state[xorIndex];
}
Buffer.BlockCopy(state, 0, buffer.Buffer, 0, 256);
key.x = x;
key.y = y;
}
private static void Prepare_key(RC4_KEY key, byte[] key_data_ptr, int key_data_len)
{
var state = key.data;;
short counter;
for (counter = 0; counter < 256; counter++)
{
state[counter] = (byte)counter;
}
key.x = 0;
key.y = 0;
byte index1 = 0;
byte index2 = 0;
for (counter = 0; counter < 256; counter++)
{
index2 = (byte)((key_data_ptr[index1] + state[counter] + index2) % 256);
var temp = state[counter];
state[counter] = state[index2];
state[index2] = temp;
index1 = (byte)((index1 + 1) % key_data_len);
}
}
