Comment by lxgr

1 year ago

"Must support 6-digit PINs" is not part of "the spec for secure credit card transaction handling" – which is also not a (or at least one) thing: There are dozens of card networks, and many of them have tons of regional variations.

In some markets, issuers only allow 4 digit PINs, and customers don't expect to have to press an "enter" key when they're done entering their 4 digit PIN – so the reasonable implementation is to allow only 4 digit PINs, or you'll be left with people staring at the ATM/POS terminal, waiting for something to happen.

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lxgr

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jiggawatts  1 year ago

4 is the minimum number of digits required, but there are over a dozen different PIN block standards, and most allow between 4..9 and 4..16 digits: https://www.eftlab.com/knowledge-base/complete-list-of-pin-b...

Making an ATM that can accept cards from multiple issuers (which is the norm these days) and allowing only 4 digits is the same category of error as requiring that the first character of someone's last name start with a capital letter, or to block symbol characters in names.

  • lxgr  1 year ago

    I agree: An annoying/avoidable implementation shortcoming, but arguably relatively orthogonal to security.

    > there are over a dozen different PIN block standards

    You almost certainly don't need to support all of these inside the PIN pad or even ATM/POS. If necessary, translation can happen in other parts of the system.