checksum

[bigfigkid]

I have researched a bit through this forum and others about checksums. From what I gather, a checksum is a summation of bytes using the xor function, and is used as a 'check' so to speak to verify that data is valid. The below lines of code are in hex format and each have a checksum I believe to be at the end of each line. I have calculated the checksum for each line using the windows calculator xor button but can't seem to get the same value.

:1000000000000000000000000000000000000000F0
:1000100000000000000000000000000000000000E0
:100020008FABC264449AFE701DE762FAB14C310690
:10003000E400526576333832005CF49C167E270566

What am I missing ?

 

[chiph]

Checksums don't always use the XOR function. They can be as complex as needed.

For example, credit card numbers have their own checksum algorithm:

http://www.beachnet.com/~hstiles/cardtype.html

Chip H.


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[strongm]

As chiph says there are numerous checksum algorithms. In this particular case, the sum of all the bytes plus the checksum sum to 0 (remembering that we are only cosidering the value of a single byte, so we ignore any carries)