Signal adds automatic key verification, a key-transparency log so you can skip the in-person safety-number ritual.
4 comments
Signal is landing on the same basic idea as CONIKS from Melara et al. 2015, with some Certificate Transparency-style auditing layered in. It finally moves the key-substitution check out of the safety-number ritual and into something the app can keep re-checking.
> Signal is landing on the same basic idea as CONIKS from Melara et al. 2015
No, that's too broad. CONIKS is an actual key transparency system with public append-only history and consistency checks, while Signal adding automated verification to a chat app is more like "don't make the user compare safety numbers by hand anymore". The part that matters here is the threat model, and that is not the same, because transparency without a strong, externally auditable log and gossip story can still just become another server-side assertion.
> It finally moves the key-substitution check out of the safety-number ritual and into something the app can keep re-checking.
Sure, but "keep re-checking" is only useful if there is a meaningful source of truth to re-check against, otherwise you're just automating the same trust-on-first-use problem with nicer UX. That is a real improvement for most users, but it is not CONIKS with some CT frosting on top.
> Signal doesn’t need to be CONIKS to inherit some of the benefit
Sure, but the benefit only lands if there is an actual log to watch, not just a nicer UI over TOFU. The comparison that feels closer to me is Certificate Transparency, with the old safety number check still there as the escape hatch.
What I’d watch for is whether the auditors and consistency checks are strong enough that a bad server can’t just serve different views forever.
coniks is the obvious reference point, but signal getting this into the app matters more than the cryptography here. the nice part is you can actually get rid of the “meet in person and read digits” ritual, which is where most people just give up and never verify anything.
compared with certificate transparency, though, the hard part is still the gossip and monitoring story, because a log that’s globally consistent only helps if split views get caught quickly. if the third-party auditors are sparse or slow, you still end up trusting the machinery around the log more than the button label suggests.