Hacker News Reader

Comment by bboygravity | Hacker News Reader

Yeah, but the client and/or server are closed source aren't they? AFAIK Signal server source code nor servers themselves are audited.

So that means all bets are off: it's entirely possible to implement a perfect peer reviewed protocol in a client and/or server full of backdoors that entirely bypasses the protocol deliberately?

View on HN

>So that means all bets are off: it's entirely possible to implement a perfect peer reviewed protocol in a client and/or server full of backdoors that entirely bypasses the protocol deliberately?

No, that's not how cryptography works. Signal clients don't trust the servers, and it's entirely possible to review the client protocol and make sure that malicious server can't learn anything about the communication (except the dreaded metadata - who talks to whom). That's the point of E2E encryption.

Clients and server are open source: https://github.com/signalapp

The protocol does not trust the server. Android has reproducible builds, iOS doesn't.

For certain things in signal you need to trust the server hardware and suspicious technologies like SGX. SGX is a prime target for a NSA backdoor. That some upper-layer software there is open source (with lots of caveats, e.g. you cannot verify which server version is really running and signal has a history of lagging behind on publishing their "open source" version of the server code) is a distraction at best.

Don't forget side-channels in SGX.

> For certain things in signal you need to trust the server hardware and suspicious technologies like SGX. SGX is a prime target for a NSA backdoor. That some upper-layer software there is open source (with lots of caveats, e.g. you cannot verify which server version is really running and signal has a history of lagging behind on publishing their "open source" version of the server code) is a distraction at best.

Before you worry about super expensive hard to remove hardware bugs, you should worry far more about the software running on that hardware. It is much more likely that theres bugs in the software than the hardware.

Yes, of course you are right. My comment was meant more along the lines of "even if the software were ultimately trustworthy because of open source, thousand eyes, careful development and fairy dust, those hardware problems would still be a way in".

Those "certain things" have nothing to do with message security. The SGX thing was an idea intended to provide a bit better protection against metadata leakage about who was talking to who. It turned out that there were other ways to get that sort of metadata. Does Signal even use the SGX stuff anymore?

Signal backup encryption works by trusting SGX. If you cannot trust SGX, you have to assume the attacker can decrypt your signal backups, of course including all media and messages.

Reply on news.ycombinator.com