2 ms·

I used to work in a bank where we had to specifically implement routines for when visa reused the PANs... There was a period between the old expiration and the

• AmericanChopper 8y ago
  I should have been a bit more verbose. Two accounts won’t have the same PAN at the same time.
  • Dylan16807 8y ago
    Which is notable, but doesn't matter in the context of "running out of numbers"
    • AmericanChopper 8y ago
      Seems to matter a lot for IPv4.
      • Dylan16807 8y ago
        Being able to recycle numbers is the difference between "this can work for a few years at full scale" and "this can work forever". IPv4 can't even reach the first level. It can't even give out one address per human. I'm sure you've seen the idea that an upgrade to IP could have just added another octet or two and changed nothing else. It would have worked pretty well to prevent us running out of addresses, with 40 or 48 bits. Well, 16 digit credit card numbers are a hair under 50 bits. And full-size 19 digit credit card numbers are a hair under 60 bits. That's plenty. You can give out a million of them to every person. If we couldn't reuse, they would eventually run out. Because we can, they won't run out.