How Credit Card Numbers Are Coded

The parity-check calculation is a challenging homework assignment; it took me three times to get it right:D

While it is interesting technically, I am unclear about the purpose of releasing such information to the general public ... more information to thiefs and crooks (nicely coined as "code breakers")!

Thanks a lot, Mint!

It's not quite giving away the farm, although it is additional information for thiefs and crooks - who unfortunately are probably already well-versed in this type of information. 

Beyond the card number, one would also need a correct valid-through date (although admittedly this has only a finite number of possibilities) and possibly a CVC as well.  Additionally, when shopping online, some retailers also validate the customer's name to the name on the card. 

That said, I would have preferred that the validating algorithm had not been published, as it is not clear what useful purpose it served to do so.
 

This is hardly the first time it's been published online.