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Crypto.cs
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Crypto.cs
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using System;
using System.Security.Cryptography;
using System.Text;
namespace PowerSpace
{
internal class RC4Context
{
private static int _SkipSize = 4096;
internal uint Pos1;
internal uint Pos2;
internal byte[] State = null;
internal RC4Context(byte[] key)
{
byte aux;
Pos1 = 0;
Pos2 = 0;
State = new byte[256];
for (int i = 0; i < 256; ++i)
State[i] = (byte)i;
for (int i = 0, j = 0; i < 256; ++i)
{
j = (j + i + key[i % key.Length]) % 256;
aux = State[i];
State[i] = State[j];
State[j] = aux;
}
Skip(_SkipSize);
}
internal void Skip(int len)
{
byte aux;
for (int i = 0; i < len; ++i)
{
Pos1 = (Pos1 + 1) % 256;
Pos2 = (Pos2 + State[Pos1]) % 256;
aux = State[Pos1];
State[Pos1] = State[Pos2];
State[Pos2] = aux;
}
}
internal void Encrypt(byte[] data)
{
byte aux;
for (int i = 0; i < data.Length; ++i)
{
Pos1 = (Pos1 + 1) % 256;
Pos2 = (Pos2 + State[Pos1]) % 256;
aux = State[Pos1];
State[Pos1] = State[Pos2];
State[Pos2] = aux;
data[i] ^= State[(State[Pos1] + State[Pos2]) % 256];
}
}
internal void Decrypt(byte[] data)
{
Encrypt(data);
}
}
}