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Comment by bozey07 | Hacker News Reader

Why is MTProto considered "home-rolled" but the Signal Protocol isn't? Both are boutique and written from scratch to fit their respective systems.

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Of course. But the history of the Signal protocol and implementation traces back 20 years. It's good enough that Facebook, WhatsApp, and Skype use it for E2EE messages. Telegram's traces back 10 years, the first version was very bad, and both versions have had a lot of scrutiny for weird design decisions.

Crypto schemes which get broken usually follow a pattern of "something smells wrong", "we have weakened it a little bit", "we have weakened it a little bit more", "this is now completely broken", "my god why are you still using MD5, it's 2017".

We're in the "something smells wrong" or "we have weakened it a little bit" phase for MTProto2, depending on how you view it.

> But the history of the Signal protocol and implementation traces back 20 years

Are you sure about that? TextSecure was created more 10 years ago than 20. 20 years ago, we did not have smartphones.

As I remember, TextSecure started with SMS (but that was not the Signal protocol) and added "internet" messages right after WhatsApp got bought (which was about when Telegram was started).

I love the Signal protocol, but I would say it's more 10 years old (like Telegram). Or am I missing something?

Signal/TextSecure (/DRA/Axolotl) has a pretty strong throughline from the "off-the-record" protocol (OTR) from 2004/2005. Signal themselves describes TextSecure as a derivative of OTR (https://signal.org/blog/simplifying-otr-deniability/).

It's close enough that if, say, a novel attack against OTR were discovered today, the first thing I'd want to know is if there are any implications against Signal.

Oh right. It does come from OTR which is 20 years old. Thanks for the clarification!

> It's good enough that Facebook, WhatsApp, and Skype use it for E2EE messages.

Wait if it's the same why don't we just use Facebook, WhatsApp and Skype instead of Signal?

It's only the protocol for their E2EE chats. There are two big caveats:

- Facebook and Skype E2EE messages are optional, and people rarely use that option, and - Those apps collect a huge amount of data outside the contents of the messages.

Still I think mentioning the greatest data collection projects in human history in the same sentence as Signal which is supposed to fight that is not very good.

Only that the protocol is an accepted standard. Very, very, very little of what's shared over Facebook is E2EE.

Why don't you go to the local casino to chat with friends? They serve the same beer.

Fair point, I've never been to a local casino but I figure the same beer will be more expensive there.

Don't forget that Signal is the name of the app, and "Signal Protocol" is the name of the E2EE protocol. The parent was talking about the Signal Protocol.

The fact that Facebook, WhatsApp, etc. use the Signal Protocol kind of shows that it is an accepted standard. But of course there are many reasons to use Signal (the App) instead of those apps, for instance:

- The Signal App is open source. You can check the protocol implementation before you use it. For Facebook, WhatsApp and Skype, you have to trust them (or some audits).

- E2EE is only one part: it ensures that nobody except the recipient can read the content of your messages. But there is a whole story around the metadata. The metadata say who writes to whom, and when. It essentially helps build a social graph. Facebook is very interested in this social graph. It would appear that the Signal Foundation is not. And even if it is not perfect, Signal does a lot to try to minimize the amount of metadata it has access to (and quite obviously Facebook has a huge incentive not to do that).

This said, IMHO it is still a lot better to use WhatsApp than to use Telegram, because at least you benefit from a good E2EE.

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