Modulo 256 (checksum)

[hentaiw]

Message : 6 23 4
Message with checksum : 6 23 4 33
Message after transmission : 6 27 4 33

This checksum simply add all bytes and append to the end of the message.

A problem with this algorithm is that it is too simple. If a number of
random corruptions occur, there is a 1 in 256 chance that they will
not be detected. For example:

Message : 6 23 4
Message with checksum : 6 23 4 33
Message after transmission : 8 20 5 33

How to calculate the change of failure actually... ?

[hanst99]

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