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Are CC numbers always unique? Or can there be multiple people with the same number but different expiry codes (or others). I always wondered if we'd run out of
by rb808 8y ago
Are CC numbers always unique? Or can there be multiple people with the same number but different expiry codes (or others).
I always wondered if we'd run out of cc numbers. 10^16 is a big number, but take out the checksums and unused blocks I'd guess we're down to only a few thousand per person.
- dsnuh 8y agoEach issuer has 1 trillion possible account numbers.[0] [0]https://www.creditcards.com/credit-card-news/credit-card-appearance-1268.php https://www.creditcards.com/credit-card-news/credit-card-app...
- anonytrary 8y agoI don't think that refutes OP's point. 10^12 is not that much, actually. That would mean that everyone in the world today gets only ~100 numbers (not even including offspring situations).
- dsnuh 8y agoThis is per issuer, so each issuer has a trillion card numbers at their disposal. Plus, the population that is eligible for credit doesn't equal total population of the planet.
- anonytrary 8y agoI see, by issuer do you mean "Visa", "MasterCard", etc.? Because there are only a handful of those. > Plus, the population that is eligible for credit doesn't equal total population of the planet. True, I'm talking about a hypothetical "maximal usage" future.
- dsnuh 8y agoThere may be only a handful that are well known, but that doesn't mean that there aren't more possible issuer numbers available. The first six digits make up the issuer identifier, so there are 10^6 possible issuers. Sure, it's not ipv6 level address space (2^128), but ~10,000,000,000,000,000 possible card numbers seems like it should last many lifetimes, especially if you consider that card numbers could be recycled/reassigned, and if we ever approached the point where running out of numbers was within imagination, we would come up with a new scheme that allowed for a few new digits. My guess is the credit card itself as a concept will be long gone before the numbers are all used up.
- anonytrary 8y agoIf the first 6 digits make up the issuer, since there are only 10 remaining digits, wouldn't that mean there are only 10^10 numbers per issuer? Where's the other factor of 100 coming from (IIRC, OP said there were 10^12)? > My guess is the credit card itself as a concept will be long gone before the numbers are all used up. I agree. Products like "privacy.com" hint that we could be approaching a "new number per purchase" meta. Even in that edge-case, if one million issuers get to have 10 billion numbers each, that would leave tens of concurrent purchases per person per issuer for an issuer with a billion users. A monopoly-level media site that lets you open a paid-subscription to multiple people could easily end up needing tens of concurrent cards per user. It seems like issuer-to-issuer number recycling would be required for sure.
- dsnuh 8y agoYou're right, I added an extra zero. It's one trillion numbers per issuer. Credit card is 18 digits, which is where the 10^12 comes from.