using System;

using System.Text;

public class Program

{

    public static string ByteArrayToString(byte[] ba)

{

  StringBuilder hex = new StringBuilder(ba.Length * 2);

  foreach (byte b in ba)

    hex.AppendFormat("{0:x2}", b);

  return hex.ToString();

}

    public static byte[] flared_47(byte[] p, byte[] d)

{

    int[] array = new int[256];

    int[] array2 = new int[256];

    byte[] array3 = new byte[d.Length];

    int i;

    for (i = 0; i < 256; i++)

    {

        array[i] = (int)p[i % p.Length];

        array2[i] = i;

    }

    int num;

    for (i = (num = 0); i < 256; i++)

    {

        num = (num + array2[i] + array[i]) % 256;

        int num2 = array2[i];

        array2[i] = array2[num];

        array2[num] = num2;

    }

    int num3;

    num = (num3 = (i = 0));

    while (i < d.Length)

    {

        num3++;

        num3 %= 256;

        num += array2[num3];

        num %= 256;

        int num2 = array2[num3];

        array2[num3] = array2[num];

        array2[num] = num2;

        int num4 = array2[(array2[num3] + array2[num]) % 256];

        array3[i] = (byte)((int)d[i] ^ num4);

        i++;

    }

    return array3;

}

    public static void Main()

    {

        byte[] data = new byte[]{0x21,0x70,0x70,0x60,0x50,0x20};

        byte[] key = new byte[]{0xaa, 0xbb, 0xcc, 0xdd};

        byte[] result = flared_47(key, data);

        Console.WriteLine(ByteArrayToString(result));

    }

}