Comment by extraduder_ire
1 year ago
Does that not cause problems on some card machines? I've come across a few that definitely don't let you put in more than four digits.
1 year ago
Does that not cause problems on some card machines? I've come across a few that definitely don't let you put in more than four digits.
Surprisingly, no, or at least it's not common.
I'm from a country that has 6-digit PINs on most cards, and I've traveled to e.g. the United States where people are surprised that credit card PINs can be more than 4 digits, but in my experience, terminals accept them just fine. It seems like they are designed to suggest a PIN is only 4 digits but they will happily accept more. So while you're entering your PIN, the display looks something like:
And then you hit OK and the PIN is accepted.
For some reason, a lot of credit card processing APIs are still oriented around physical card machines, so they have a lot of fields devoted to self-declaration of the available features.
Some of the APIs allow the machine to say "I can accept a PIN up to 12 digits".
However, I don't know if anyone 1) actually delivered on it and 2) how you'd know in advance just poking random devices in stores.
That provides very valuable information: DO NOT TRUST this machine to be secure!
Similarly, any web site or app that can’t correctly handle a space character at the end of the password should never be trusted with anything of consequence.
Why? PINs are limited to 4 digits in many markets, so it's not exactly extreme for a developer to not consider the (to them) edge case of 6 digit PINs on foreign cards.
Conversely, it seems very possible to support 6 digit PINs and yet still make a ton of horrible implementation mistakes, security and otherwise.
Why is the space thing inherently insecure? I’m thinking bad form validation could trip it up and be considered “not handled” vs concerns suggesting plaintext storage
Are you really worried that a card machine is going to leak your PIN? That doesn't seem to be a common attack vector compared to a third-party skimmer being attached or someone just mugging you and demanding your PIN under threat of physical violence.
To answer the actual question: I don't know because I left my PIN at 4 digits, despite knowing I could use more, precisely because I didn't think it would really make my life any more secure.
I'm not worried specifically about the PIN leaking.
The concern is that a 4-digit max PIN length is certainly implemented by someone who couldn't be bothered to read the spec for secure credit card transaction handling.
It's the equivalent of the "No brown M&Ms" clause or "Canary in the coal mine" test.
Nobody actually cares about the M&M color or some dumb bird.
8 replies →
It most certainly does.