(49G) Verhoeff Check Digit Programme

[Thomas Klemm]

Very cool! This algorithm is based on multiplication in the dihedral group D₅ which is not commutative. This allows to detect all transposition errors involving two adjacent digits.
There was a project where I decided to use this as the checksum digit for a numeric user ID which forced some batch-programmers to implement it in COBOL. They were not amused.

Cheers
Thomas