Fletcher's checksum

Fletcher's checksum is one of several types of checksum algorithms, which are relatively simple processes used by computers to check the integrity of data.

It is designed to overcome some of the inadequacies of simply summing all the bytes as in the original checksum. Fletcher's checksum, unlike the original checksum, can detect the inserting/deleting of zero value bytes, the reordering of bytes, and incrementing and decrement of the bytes in opposite directions.

Fletcher's checksum is defined in RFC 1146.

Adler-32 is an improved version of Fletcher's checksum.