5 ms·

This probably depends on where you are using it. If I understand correctly, it tells an attacker that you have _something_ to hide, but gives no clue as to any

by hbrav 5y ago

This probably depends on where you are using it. If I understand correctly, it tells an attacker that you have _something_ to hide, but gives no clue as to any metadata, such as the size of what you're hiding or how often it was updated. Suppose a government agency is demanding that you decrypt... something, they're not sure what, or how much there is, or even if there's anything there. In a country with a strong rule-of-law, I think you're unlikely to have a court enforce sanctions against you to make you produce cleartext _that may not even exit_, unless they have very strong evidence from another source that it does exist. If you're in a more authoritarian country where the police can hold you for a long time just on the off-chance that there's more cleartext to get, then I don't think this helps you much. Actually, I think we can maybe summarize: you probably shouldn't use this to defend against someone who would have no qualms just straight-up torturing you.

arcticbull 5y ago
> This probably depends on where you are using it. If I understand correctly, it tells an attacker that you have _something_ to hide, but gives no clue as to any metadata, such as the size of what you're hiding or how often it was updated. Which brings you right back to the problem illustrated in the XKCD comic up top. As soon as you know they have something to hide you whack them until they tell you.
- giaour 5y ago
  There is still some value in being able to disclose some private data without disclosing whether further private data exists. The other party will not know after a revelation if they have obtained the totality of secret data and must decide whether to continue to hit you with the wrench on the off chance that more secret data exists. This is a well known dilemma when interrogating people, since there's no known metadata about how many facts exist in your brain. As the GP points out, though, a common authoritarian response to this dilemma is to just keep torturing.
- dividedbyzero 5y ago
  Depending on where you are and what specific laws are in place that someone (the police maybe?) may not be able to get more whacking past a judge. I think this could work reasonably well in such situations.
  - arcticbull 5y ago
    Here’s the problem. In a rule of law jurisdiction there’s no value provided. In one without they’ll just hit you.
- throwaway22032 5y ago
  So you tell them. How do they know you've told them everything?
  - arcticbull 5y ago
    Whack harder.
    - deleted 5y ago
      [deleted]
ansible 5y ago
I agree with all that. The only way something like PDDB would work in practice to help the people intended, is for the software to become very widely used. For example, where everyone stores their pornography in a PDDB. In that case, you would also store some porn in your PDDB, and would give up the password to that with little coercion. If they can't then prove the existence of more information, then you might be let go without too much damage. Obviously, you shouldn't be storing porn that is illegal in your (or most other) jurisdictions in the first level of your PDDB. In any event, good luck trying to get even a fraction of normal users to install and use this software. Even if all the Linux distros include it by default, I don't think that would be enough, that would just widen the target to "all Linux users" in oppressive country A.
- cryptonector 5y ago
  Widespread use does not help the user: whoever wants their secrets will still insist on production of ever more secrets whenever the user is found to be using a PDDB. Widespread use can only help if that widespread use leads the State to accept it and that it should not insist on production of secrets from PDDBs. However, how likely do you think that would be??
  - ansible 5y ago
    > Widespread use can only help if that widespread use leads the State to accept it and that it should not insist on production of secrets from PDDBs. However, how likely do you think that would be?? Not likely. At this point, if you want to hide secrets from the state, I think you'd be better off finding some place to stash a micro-SD card. Those things are so tiny and easy to lose in the best of circumstances...
gampleman 5y ago
It could even make things much worse for you. If you have a standard encryption scheme then the torturer can be reasonably sure that they got everything useful out of you and can stop torturing you. On the other hand if you are running PD software, then even if you had nothing particularly important to hide (gasp, they now have my Facebook password!), they might as well continue torturing you since there is no way to show that really you don't have those stolen Death Star plans.
- pessimizer 5y ago
  The problem with torture is that in that case you also have no reason to give them a correct answer, no matter how much they hurt you.
  - cryptonector 5y ago
    That's not the case here. Here they have a way to confirm that what you gave them produced more meaningful plaintext. And considering how large this PDDB might be, you might never be able to give them enough passwords to produce as much meaningful plaintext as could have been stored in it. Therefore they might never be satisfied that you have produced all of the meaningful plaintext plausibly stored in the PDDB. You might as well say that giving the user plausible deniability also means giving their adversary plausible never-reaching-the-end-of-the-barrel. The former is good for the user if and only if the adversary is willing to pretend the PDDB thing isn't a thing, but why would they? No, plausible deniability tools are not useful to most users. They are plausibly useful to a class of users (spies?) who might have resources or recourse to leverage that can be used to a) get them set free, b) without much or any torture, and c) without having to reveal their secrets. That class of users must be very small.
    - gampleman 5y ago
      I don't think that's a fair conclusion either though. Torture resistance is just one of many security properties someone might care about and for most people it's really not the biggest worry. The PD aspect might be a lot more useful in a more lawful coercion setting or a setting with more limited coercive access (i.e. a mugger threatening you with a knife on a street - can't afford to torture you for days just in case you're hiding something more).

by hbrav 5y ago

arcticbull 5y ago

> This probably depends on where you are using it. If I understand correctly, it tells an attacker that you have _something_ to hide, but gives no clue as to any metadata, such as the size of what you're hiding or how often it was updated. Which brings you right back to the problem illustrated in the XKCD comic up top. As soon as you know they have something to hide you whack them until they tell you.

giaour 5y ago
There is still some value in being able to disclose some private data without disclosing whether further private data exists. The other party will not know after a revelation if they have obtained the totality of secret data and must decide whether to continue to hit you with the wrench on the off chance that more secret data exists. This is a well known dilemma when interrogating people, since there's no known metadata about how many facts exist in your brain. As the GP points out, though, a common authoritarian response to this dilemma is to just keep torturing.
dividedbyzero 5y ago
Depending on where you are and what specific laws are in place that someone (the police maybe?) may not be able to get more whacking past a judge. I think this could work reasonably well in such situations.
- arcticbull 5y ago
  Here’s the problem. In a rule of law jurisdiction there’s no value provided. In one without they’ll just hit you.
throwaway22032 5y ago
So you tell them. How do they know you've told them everything?
- arcticbull 5y ago
  Whack harder.
  - deleted 5y ago
    [deleted]

ansible 5y ago

I agree with all that. The only way something like PDDB would work in practice to help the people intended, is for the software to become very widely used. For example, where everyone stores their pornography in a PDDB. In that case, you would also store some porn in your PDDB, and would give up the password to that with little coercion. If they can't then prove the existence of more information, then you might be let go without too much damage. Obviously, you shouldn't be storing porn that is illegal in your (or most other) jurisdictions in the first level of your PDDB. In any event, good luck trying to get even a fraction of normal users to install and use this software. Even if all the Linux distros include it by default, I don't think that would be enough, that would just widen the target to "all Linux users" in oppressive country A.

cryptonector 5y ago
Widespread use does not help the user: whoever wants their secrets will still insist on production of ever more secrets whenever the user is found to be using a PDDB. Widespread use can only help if that widespread use leads the State to accept it and that it should not insist on production of secrets from PDDBs. However, how likely do you think that would be??
- ansible 5y ago
  > Widespread use can only help if that widespread use leads the State to accept it and that it should not insist on production of secrets from PDDBs. However, how likely do you think that would be?? Not likely. At this point, if you want to hide secrets from the state, I think you'd be better off finding some place to stash a micro-SD card. Those things are so tiny and easy to lose in the best of circumstances...

gampleman 5y ago

It could even make things much worse for you. If you have a standard encryption scheme then the torturer can be reasonably sure that they got everything useful out of you and can stop torturing you. On the other hand if you are running PD software, then even if you had nothing particularly important to hide (gasp, they now have my Facebook password!), they might as well continue torturing you since there is no way to show that really you don't have those stolen Death Star plans.

pessimizer 5y ago
The problem with torture is that in that case you also have no reason to give them a correct answer, no matter how much they hurt you.
- cryptonector 5y ago
  That's not the case here. Here they have a way to confirm that what you gave them produced more meaningful plaintext. And considering how large this PDDB might be, you might never be able to give them enough passwords to produce as much meaningful plaintext as could have been stored in it. Therefore they might never be satisfied that you have produced all of the meaningful plaintext plausibly stored in the PDDB. You might as well say that giving the user plausible deniability also means giving their adversary plausible never-reaching-the-end-of-the-barrel. The former is good for the user if and only if the adversary is willing to pretend the PDDB thing isn't a thing, but why would they? No, plausible deniability tools are not useful to most users. They are plausibly useful to a class of users (spies?) who might have resources or recourse to leverage that can be used to a) get them set free, b) without much or any torture, and c) without having to reveal their secrets. That class of users must be very small.
  - gampleman 5y ago
    I don't think that's a fair conclusion either though. Torture resistance is just one of many security properties someone might care about and for most people it's really not the biggest worry. The PD aspect might be a lot more useful in a more lawful coercion setting or a setting with more limited coercive access (i.e. a mugger threatening you with a knife on a street - can't afford to torture you for days just in case you're hiding something more).