[Cryptography] Rubber-hose resistance?

[Erwan Ounn]

> On Nov 27, 2017, at 19:35, erik <erik at erikgranger.name> wrote:
> 
> I was talking recently with a few buddies, and the idea came up that there
> ought to be a Trezor or Ledger-type wallet out there that somehow won't work
> if you have an exceedingly high heart rate, combined with some other sort of
> indicator.  The idea was that if someone ever wanted to steal your bitcoins,
> they could do it by scaring you into just sending them your bitcoins. If,
> however, people set up a wallet that wouldn't let them spend their bitcoins if
> they were under duress, using some menagerie of biometric indicators for
> authentication as well as duress detection, that this might make it harder for
> people to mug bitcoin owners.
> 
> I think this might become a problem in the future as the IRS tries cracking
> down; lots of people out there might not have washed their coins correctly,
> and the price of coin-mixing is going through the roof with the tx fees, so it
> makes sense that in the future nefarious state actors such as IRS agents might
> try to conduct rubber-hose crypto-analysis to gain unwanted access to your
> holdings.
> 
> What do you guys think?
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I agree that there ought to be better ways to protect your stash.

With that said, I don’t think the system you outlined would achieve that goal. It basically comes down to the fact that sensory data can be forged and sensors fooled, for cheap. In addition to that, if a robber has physical access to you and is in position to do you harm then what prevents them from sedating you?

In my opinion, a better system is one whose security do not depend on your final say at the time of the robbery. That is, you could by construction limit the withdrawal of more than a certain amount of coins every N days (a vault). The settings of such a system could be controlled by an “overwrite key” that is split among a college of trusted third-parties. Together, you would be allowed to edit the settings (threshold, lock-period etc.) which would only be applied after a certain period of time and over which you have a veto.

Let me know what you think,
— Erwan
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