Well no, that's not true - a bank could issue you with a one-time-pad long enough to encrypt the next 10000 messages with you, and use that over the years - they just need to tell you which line of the key is needed to decrypt your message. In that scenario you only need to guarantee security for the first time the key is distributed(for example a file sent to you when the account is opened).

You’d have to guarantee security every time a key is distributed, right? I guess practically it would look like going to the bank every few years… or maybe only once per account, you can fit a lot of bank statements in a couple gigabytes.

Actually this could be a nice service to offer now. We might worry that someday public key crypto will be broken, and we wouldn’t want all our old bank statements to become public at that point I guess.

I mean, years ago my local bank had an online banking system, where your PC had to dial-up their local server for any operations - and the authentication key was on a floppy. Which meant that yes, you needed to visit their branch once every year for a new key distributed on this physical medium.

Yes, it was inconvenient, but hardly an impossible thing to do. Banks manage to communicate the PIN for your card safely every time you open an account, I'm sure this could be done as well.

So now people have to keep a piece of paper around or somehow put it into some software and not lose access. You're right, it would work. In reality, people can't even be bothered to use a password manager or understand even the most simple of new security software, let alone even remember their password. That makes it completely intractable as a solution.

I mean, the scenario being discussed here is some kind of "world ending" situation where all known encryption is broken. So you either do it the way I described it, or you don't have any encryption whatsoever. I think under those conditions people would adjust. It isn't an alternative to our current arrangements.

Also: my bank access is done entirely through an app that obscures its internal implementation. It could already be using OTP and it wouldn't make any difference to me, nor would I be able to tell(my point is that the user wouldn't need to keep a piece of paper that they would need to type in anywhere - the internal implementation of tools we use every day would change, but most users wouldn't even notice)

I’m not clear on how we’d use a one-time-pad on a physical piece of paper (unless we want to do it like an old-timey spy novel character, using pencil and paper to combine the bits!)

Concur. I should have stated "an argument" not "the argument".