> I would place Signal in the same tier as WhatsApp here (Tier 2). They both upload your contacts to an intermediate server that gives you their public key, whi

> I would place Signal in the same tier as WhatsApp here (Tier 2). They both upload your contacts to an intermediate server that gives you their public key, which you can optionally verify afterwards. The last time this came up, inspired by a post by pbsd, I submitted a detailed write-up of a protocol Signal could use to avoid requiring users to submit their contact information: https://news.ycombinator.com/item?id=11289223 https://news.ycombinator.com/item?id=11289223 It's a solved problem. > A messenger that really did "all possible tradeoffs in favor of security" would force you to verify the recipient, either in person or via a web of trust. I think not doing that is a perfectly acceptable tradeoff to protect 1 billion users from passive mass surveillance. Except it introduces another point of security failure. I would prefer to use a system like SDSI/SPKI's friend-of-a-friend naming, with a contact-sharing mechanism so that I could, say, know that I was talking to 'Sheila's Dad' or 'My Boss's Jim's Phone' (presented in a somewhat more user-friendly way, maybe 'My Boss → Jim → Phone' or something).