Cloudflare and Trail of Bits are serving as the key transparency auditors.
This only works if you know the contact’s phone number.
More details in the post.
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It seems it still relies on a secondary channel to some degree.
For Signal’s implementation of key transparency, Cloudflare and Trail of Bits serve as trusted third-party auditors.
So, it’s a permissioned set of approved auditors rather than it being open to the public i.e. anyone who chooses to put in the work? Not good if so. How do we know that they are trustworthy either? WhatsApp, if I remember correctly, had auditing open to the public.
Haven’t read the technical details yet.
I actually find that metaphors and analogues like the one they’re using about a ledger don’t really help me understand. I guess I’m still none the wiser than when I tried to watch talks and read academic papers to understand WhatsApp’s version.
Maybe the draft IETF spec will help.
I will continue to rely on verifying safety numbers.
There’s no cryptographic magic sauce here. It’s just two CAs writing to signed append only ledger. If you don’t want to trust CloudFlare and Trail of Bits, you should verify the safety numbers manually, preferably face to face.
The challenge here is Signal has only a toggle for key trust level, so you need to adopt a manual way to keep track of the method and trust level used.
Easy way is to just come up with your own scheme of authentication levels and send a message to the chat containing a keyword for the procedure “fp-verification” or whatever you want, part of the safety number as a way to tie that safety number to the method which will be the third field. You can then check it with search.
I would recommend you to only tap Signal’s own verified toggle once you feel the authentication level is adequate for the conversation. So for example if it’s a close friend or trusted work partner or whatever, be sure to use automatic check immediately, call when you have time, and to toggle it only after you find time to meet and scan it face to face. If it’s a distant friend of a friend, you might just toggle it after using this new TTP approach.
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