5 ms·

Maybe we can design one using https://www.btproof.com/ https://www.btproof.com/ ? That system lets us permanently store timestamps with roughly hourly precisio

by jzwinck 13y ago

Maybe we can design one using https://www.btproof.com/ https://www.btproof.com/ ? That system lets us permanently store timestamps with roughly hourly precision along with 160 bits of arbitrary data. This would let us, for example, find the (earliest) time a password was set, so we could know if it is too old. But there's still a lot to be figured out here, and I'm no cryptanalyst. For starters, can the decryption system know it is seeing the "real" Bitcoin blockchain and not that of an interloper?

tlrobinson 13y ago
If someone has a copy of the encrypted file on hardware they control then there's absolutely no way to prevent them from modifying the software/RAM to fool the decryption routines into using a fake timestamp/blockchain/whatever. You'd need tamper-proof hardware.
- malandrew 13y ago
  I reckon you could make hardware tamper-proof by setting the hardware in a booby-trapped container that would self-destruct if tampered with. Make sure that the only two connections coming out of the booby-trapped container are power and a data connection over which the memory of the device cannot be accessed, such as ethernet.
- rdl 13y ago
  You could build something where the human never had the actual key. The human has a passphrase which goes to a piece of hardware with the actual key, either tamper-responding physical hardware with a clock, or some kind of network service (e.g. a .onion service) which takes the user's passphrase and returns a key. As long as the user (or subverted hardware) doesn't retain the actual key each time, it's probably ok, and protected from this particular case of compelled disclosure. The ideal is to use some kind of tamper-responding hardware to process the data (as well as decryption), though. And probably locally -- I don't think I'd trust an .onion service to stay up if it disappearing meant I would no longer have access to my files.

by jzwinck 13y ago

tlrobinson 13y ago

If someone has a copy of the encrypted file on hardware they control then there's absolutely no way to prevent them from modifying the software/RAM to fool the decryption routines into using a fake timestamp/blockchain/whatever. You'd need tamper-proof hardware.

malandrew 13y ago
I reckon you could make hardware tamper-proof by setting the hardware in a booby-trapped container that would self-destruct if tampered with. Make sure that the only two connections coming out of the booby-trapped container are power and a data connection over which the memory of the device cannot be accessed, such as ethernet.
rdl 13y ago
You could build something where the human never had the actual key. The human has a passphrase which goes to a piece of hardware with the actual key, either tamper-responding physical hardware with a clock, or some kind of network service (e.g. a .onion service) which takes the user's passphrase and returns a key. As long as the user (or subverted hardware) doesn't retain the actual key each time, it's probably ok, and protected from this particular case of compelled disclosure. The ideal is to use some kind of tamper-responding hardware to process the data (as well as decryption), though. And probably locally -- I don't think I'd trust an .onion service to stay up if it disappearing meant I would no longer have access to my files.