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Comment by gleenn | Hacker News Reader

Isn't the problem with one time pads distributing the pad? Like, you would have to walk to a bank and have them hand you a piece of paper... and tellers could read the paper before handing it to you. So basically so ineffective in practice as to be unusable?

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The distribution part have gotten a lot easier. I would be very possible for banks to give all their customers USB devices with a few GByte of one time pads and keep a copy of those same GBytes in their own systems.

And most banks still have brick-and-mortar stores where customers could come and identify themselves and collect their one time pad.

And a GByte of keypads would cover your banking need for a long time.

The problem is more that it works for some one-to-many relationsships such as banks, but not many-to-many relationships, such as emails, websites, etc. There have to be second or third parties.

On the hand, a lot of people seems to log in everywhere with Google Sign In or similar anyway.

And we could instead all have Google or Amazon devices with GBytes of one time pads. And that could be used to set up symmetric encryption, which should be more resistant to quantum computer attacks.

The only drawback is that we would have to trust the third party and everyone who could compromise the third party and every government that could put pressure on the third party :-)

Quantum Key Distribution. You can prove that the key hasn't been intercepted. But since that means you need a direct point to point connection with no routers, switches, hubs, amplifiers/repeaters etc., it only works for a tiny fraction of cases. https://en.wikipedia.org/wiki/Quantum_key_distribution

I remeber in the very early 2000s, a guy had a stopwatch sized whos-it, and it kept flashing numbers on it. Updated every 5 minutes.

Apparently, some cesium based list of numbers, again, was 20 years ago.

Point is, it was a one time pad...

You mean this? https://en.wikipedia.org/wiki/RSA_SecurID I'm not sure but I don't think this is OTP?

Indeed, they're not one-time pads - they are symmetric authenticators where both sides hold the same seed, and iterate a PRNG or similarly iterable function every N units of time (say, 30 seconds), to give you the same new output, based on the same starting seed. Think stream cipher output, with an initialisation vector.

They are often called OTPs though (i.e. one-time passcodes), just to cause confusion.

A Whatsit. A Thingamabob. A doohickey. I remember those - people still use them I think?

so print it via pressure into the inside of a sealed envelope? that's how they send me my PIN.

(not sure if replying to troll..)

The argument against OTP is that by securely distributing the key of the same length as your message, you ostensibly already have a secure messaging mechanism; why would you need the OTP?

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".

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