On Sun, Mar 22, 2020 at 5:43 AM Tim Ruffing <cry...@timruffing.de> wrote:
> On Sat, 2020-03-21 at 12:59 -0400, Russell O'Connor wrote: > > Public keys are deterministic and can be spot checked. In fact, > > AFAIU if hardened HD key derivations are not used, then spot checking > > is very easy. > > > > While spot checking isn't ideal, my original concern with the > > synthetic none standard proposal was that it is inherently non- > > deterministic and cannot ever be spot checked. This is why anti- > > covert signing protocols are so important if we are going to use > > synthetic nonces. > > If spot checking means checking a few instances, then I think this is a > pretty weak defense. What if the device starts to behave differently > after a year? > I agree, which is why there perhaps is merit in using a non-hardered derivation path so that the software side of a hardware wallet can check the pubkey. Though I understand there are some disadvantages to the non-hardened paths. However, spot checking can even be done retroactively (and thoroughly). Again, I agree that this is less than ideal, but does let you take some action once you notice a deviation. Your claim is that if we don't fix the pubkey issue there is no point in fixing the signature issue. I disagree. While I think both issues need to be fully addressed, the issues around the original proposed non-deterministic signature scheme are far more severe. The proposal would move us from a deterministic scheme, where spot checks are possible, with all the caveats that entails, to a non-deterministic scheme where spot checks are impossible. My hope is that we can standardise a scheme that has the advantages of non-determinism without the threat of covert channels.
_______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
