6 ms·

In the worst possible case we just switch to the one time pad encryption, which makes things inconvenient but literally can't be cracked by any computer or algo

In the worst possible case we just switch to the one time pad encryption, which makes things inconvenient but literally can't be cracked by any computer or algorithm(tldr: the length of the key is as long as the length of the message, so a message can decode into anything and you can't tell whether the text you decoded is the right one or not). So a scenario where literally no encryption is available seems far fetched.

tptacek 4y ago
There's any number of less subtle and more important problems with this idea, but another problem you have here is that one-time pads only provide confidentiality, not integrity.
codethief 4y ago
> we just switch to the one time pad encryption "just". So how do you do the key exchange?
- grogenaut 4y ago
  Email it obviously
- gambiting 4y ago
  Depends on the security of the service you want to use - I'd expect my bank or my email provider to send me my encryption keys by a recorded letter. Hacker news can probably email me their key instead. Again, we're talking about some "world ending" scenario that OP mentioned - where all "normal" forms of encryption are already broken. If OTP is the only unbreakable encryption around, them I'm sure we'd find a way to distribute keys.
gleenn 4y ago
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?
- nelgaard 4y ago
  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 :-)
- armb 4y ago
  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 https://en.wikipedia.org/wiki/Quantum_key_distribution
- b112 4y ago
  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...
  - dekhn 4y ago
    You mean this? https://en.wikipedia.org/wiki/RSA_SecurID https://en.wikipedia.org/wiki/RSA_SecurID I'm not sure but I don't think this is OTP?
    - 4y ago
idiotsecant 4y ago
Yes, we simply change to one time pad encryption and ... distribute pre-share keys to every user on earth for every service that modern civilization relies on? The failure of RSA in a significant way would mean the end of modern commerce, military balance of power, and the sharing of information. It would be a history-altering event in the best case and devolve into existential war in the worst case. OTPs would do exactly zero to prevent any of that.
- gambiting 4y ago
  >>OTPs would do exactly zero to prevent any of that. So if it was literally the only remaining unbroken type of encryption on the planet, it would have no effect? How so, exactly? We would just go with no encryption whatsoever rather than bear the inconvenience of distributing OTP keys?
- retrocryptid 4y ago
  As a reminder, "mekmiditastigoat" is the internet shared secret for IPSec interoperability. In a pinch you can use it for SSH as well.
- tptacek 4y ago
  Not really. The failure of RSA would necessitate a rapid shift to, probably, lattice key exchange. It would be a fire drill, but it would be greater by degree and perhaps not by kind than previous fire drills we've run.

tptacek 4y ago

There's any number of less subtle and more important problems with this idea, but another problem you have here is that one-time pads only provide confidentiality, not integrity.

codethief 4y ago

> we just switch to the one time pad encryption "just". So how do you do the key exchange?

grogenaut 4y ago
Email it obviously
gambiting 4y ago
Depends on the security of the service you want to use - I'd expect my bank or my email provider to send me my encryption keys by a recorded letter. Hacker news can probably email me their key instead. Again, we're talking about some "world ending" scenario that OP mentioned - where all "normal" forms of encryption are already broken. If OTP is the only unbreakable encryption around, them I'm sure we'd find a way to distribute keys.

gleenn 4y ago

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?

nelgaard 4y ago
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 :-)
armb 4y ago
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 https://en.wikipedia.org/wiki/Quantum_key_distribution
b112 4y ago
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...
- dekhn 4y ago
  You mean this? https://en.wikipedia.org/wiki/RSA_SecurID https://en.wikipedia.org/wiki/RSA_SecurID I'm not sure but I don't think this is OTP?
  - 4y ago

idiotsecant 4y ago

Yes, we simply change to one time pad encryption and ... distribute pre-share keys to every user on earth for every service that modern civilization relies on? The failure of RSA in a significant way would mean the end of modern commerce, military balance of power, and the sharing of information. It would be a history-altering event in the best case and devolve into existential war in the worst case. OTPs would do exactly zero to prevent any of that.

gambiting 4y ago
>>OTPs would do exactly zero to prevent any of that. So if it was literally the only remaining unbroken type of encryption on the planet, it would have no effect? How so, exactly? We would just go with no encryption whatsoever rather than bear the inconvenience of distributing OTP keys?
retrocryptid 4y ago
As a reminder, "mekmiditastigoat" is the internet shared secret for IPSec interoperability. In a pinch you can use it for SSH as well.
tptacek 4y ago
Not really. The failure of RSA would necessitate a rapid shift to, probably, lattice key exchange. It would be a fire drill, but it would be greater by degree and perhaps not by kind than previous fire drills we've run.