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0 pointsdsnuh7y ago0 comments

There 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.

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anonytrary7y ago· 1 in thread

If 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.

dsnuhOP7y ago

You'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.

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