checksum code in c#

using System;

using System.Text;

class Program

{

   static byte crc8(byte[] str) // no need to pass length in 'safe' code

   {      

      int len = str.Length;

      int i, f;

      byte data;

      byte crc;

      crc = 0 ;

      int j = 0;

      while (len-- != 0)

      {

        data = str[j++];

        for(i = 0; i < 8; i++)

        {

           f = 1 & (data ^ crc);

           crc >>= 1;

           data >>= 1;

           if (f != 0)    

           {

             crc ^= 0x8c;

           }

        }

      }

      return crc;

   }

   static void Main()

   {

      string s = "The quick brown fox jumps over the lazy dog"; 

      byte[] str = Encoding.ASCII.GetBytes(s);

      byte crc = crc8(str);

      Console.WriteLine(crc);

   }

}

The programs are of course computing a 'cyclic redundancy check' which is often used for checksums and the like.

If you need to understand the mathematics of how this works, I'd check out this Wikipedia article and follow the associated links:

http://en.wikipedia.org/wiki/Cyclic_redundancy_check