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The Math Hack You Didn’t Know Was in Your Credit Card
(www.scientificamerican.com)
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this post was submitted on 12 Aug 2025
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Technology
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I’m insulted they thought I didn’t know what a LUHN check is.
Of course, my current credit cards don’t even have a magnetic stripe, so the original purpose for the check digits is history. Still useful for other situations where the number might get garbled though.
The other thing useful about credit cards is that the first set of digits refer to the issuer, not your account. Once you strip off the issuer code and the check digit, there’s much less that’s unique to your card.
The check digit is to catch a mistyped number.