[erlang-questions] checksum calculation

[Gamoto]

Richard,
Suppose you have an industrial machine which send messages following by the checksum calculated by the xor of all bytes, what can I do with your advices ;-)
John
>
>On 6 Apr 2009, at 9:34 pm, Gamoto wrote:
>
>> If it is not a very good solution, would you like to suggest a  
>> better one, for me and the other readers ?\
>
>Suppose you have a block of bytes and there is an
>error that results in one byte being replaced by
>a different byte.  Then an XOR checksum will detect
>that difference.
>
>Suppose there is an error that results in two bytes
>being swapped.  Then an XOR checksum will detect no
>change at all.  Or suppose that two equal bytes are
>both replaced by the same new byte.  Again, nothing
>noticed by XOR.
>
>Just look "checksum" up in the Wikipedia; that's as
>good a place as any to start.
>
>The 'zlib' module in Erlang already has support for
>crc32 and adler32.  I thought I saw crc32 somewhere
>else as well.
>
>Theory and practice don't agree as much in practice
>as they do in theory, so it's worth having a look at
>"Performance of Checksums and CRCs over Real Data"
>by Jonathan Stone, Michael Greenwald, Craig Partridge,
>and Jim Hughes
>and at "Revisiting Fletcher and Adler Checksums"
>by Theresa Maxino, whose conclusions I found surprising.
>
>It all depends on what your data are like and what
>kinds of errors you plausibly need to protect against,
>really.
>
>