Hacker News Reader

Assuming you’re using Signal for organizing something the government doesn’t want you organizing, if one member of the group gets rubber-hosed into unlocking their phone, the govt instantly gets a list of verifiably correct names of people involved. In contrast, with a service that lets you use usernames that maneuver would reveal nothing but those usernames (which are as pseudonymous as it gets).

One of the other problems with using phone numbers, is that it provides an opening for adversaries. Now they know your phone number, which can be used for social-engineering attacks to attempt to bypass 2FA for any other online services tied to your phone number. Either for 2FA or for account-recovery/i-forgot-my-password functionality. 2FA by SMS is wrong and broken and nobody should use it, but they do.

Adversaries will attempt to social engineer customer service for your phone carrier into issuing them a new SIM or porting out the number, so they can receive verification SMS and phone calls.

Signal uses a registration pin to prevent that exact attack.

Maybe I misread, but the GP doesn't seem to be talking about impersonating a user on Signal, but rather impersonating that user on other websites that depend on SMS 2FA sent to their phone number that is now visible through Signal.

Thanks - the concern makes sense to me given that context.

I feel comfortable with giving my Telegram username out to random people on the internet and posting it on my website because it doesn’t mean anything outside of Telegram. I wouldn’t post my phone number publicly.

That’s fair, thanks - I think for secure communication with people you don’t know personally or trust, it’d be better to use something that doesn’t share your phone number.

> roll their own cryptography

Signal did the same thing. They invented their own cryptographic algorithms. https://en.wikipedia.org/wiki/Double_Ratchet_Algorithm

And the social graph IS sent to servers by Signal. It's protected only by hashing (trivial to circumvent) and by the Intel SGX technology (a bit harder to circumvent, but I doubt that the US govt can't do it).

Signal's crypto is an incremental improvement of existing algorithms with good reputation, OTR and SCIMP.

Telegram's crypto is reportedly designed from scratch, with questionable choices such as SHA1 and MAC-then-encrypt.

https://www.cryptofails.com/post/70546720222/telegrams-crypt...

https://eprint.iacr.org/2015/1177.pdf

I didn't want to claim that Telegram's crypto was better or as good as Signal's. But saying that Telegram rolled their own crypto while Signal did not is misleading as both designed their own protocols.

Also, Telegram uses SHA256 now in the places relevant for security, so that point was resolved.

My (limited) understanding is numbers are queried to see if accounts exist, but those queries are not connected to the users sending them (and they are obscured in transit).

Am I wrong?

Signal’s cryptography has also gotten a ton of attention, I don’t think the same is true for competitors.

Transit encryption is employed by other services as well. Whether there is de-correlation on the cloud backend I don't know. Maybe there is, but you can't really verify that and it's easy to correlate them again, especially if clients use ipv6 or non-CGNAT ipv4.

>If that’s the case doesn’t it matter even less that signal requires it since it’s already known anyway?

Well, if you're operating on that premise, which is to say, a premise of complete and total resignation and surrender, then from that starting point of course you haven't lost anything. I don't think anybody is joining you though in agreeing that that's a legitimate starting place to analyze privacy concerns associated with the phone number requirement.

This is such an uncharitable interpretation of what I was saying that it's basically a straw man.

If you're required to use ID to get a SIM (as K2L8M11N2 stated in the parent comment I replied to), then what I was saying follows - that the person is already tied to the phone number anyway.

In this context Signal revealing the only data they have (that a phone number signed up on X day) really doesn't matter or reveal anything new.

K2L8M11N2's other response to my comment is a helpful clarification, it's less about what can be compelled from Signal the company and more about what can be turned over if a user's device is compromised. In that context the name to number connection is more serious because they also have the content.

I'm sorry but absolutely nothing about this is a straw man or uncharitable, and I'll explain why.

>If you're required to use ID to get a SIM (as K2L8M11N2 stated in the parent comment I replied to), then what I was saying follows

Yes, and this is what I was responding to. You want that "if" to be taken for granted as an unchallenged starting premise to your entire argument. And that amounts to a massive privacy concession. And the fact that I'm challenging that premise, and bringing up the privacy concerns that are associated with that "if", that is the thing that you're describing as uncharitable. Even though you don't appear to dispute that it is indeed a privacy concession. And it only follows if you don't contemplate alternatives to using a phone number, which is what I took to be their point about the problems associated with a phone number.

>and more about what can be turned over if a user's device is compromised. In that context the name to number connection is more serious because they also have the content.

That's going true in any context where your number can be revealed, which is why it has unique disadvantages that usernames wouldn't have, under any conceivable hypothetical scenario. I'm glad that you benefited from their clarification but that struck me as a truism about the nature of phone numbers versus the nature of usernames.

> "You want that "if" to be taken for granted as an unchallenged starting premise to your entire argument."

I don't want that 'if' to be anything. It was the premise, because the parent comment I was responding to was stating it as a fact for where they live.

My point is that signal revealing your phone number and when you signed up doesn't reveal anything new about you. The issue is the case K2L8M11N2 mentioned when they have compromised a device (and can now tie content to IDs via the phone number).

> "That's going true in any context where your number can be revealed...under any conceivable hypothetical scenario."

This is just false? Without access to the content on a compromised device a phone number alone doesn't reveal much (that's the entire point of the e2ee), if it limits the ability for Signal to hand over the social graph or any other metadata (which does reveal a lot) that seems like a win.

Obviously revealing the phone number still reveals more than a username would, and if you can get all the benefits of not having to upload your social graph to their servers or share metadata without having to use phone numbers that would be better - I think they're working on that.

People using apps that upload their social graph and collect their metadata so they don't have to use their phone number are probably making the wrong choice when considering the trade-offs.

"The social graph" (your phone book) is most likely already uploaded somewhere by third-party app or even Google/Apple themselves. Using separate contact list (even uploaded to some server) seems more secure to me than using your phone's one.

The phone number is much more valuable to any authority than other metadata because they are more likely to have access to cell service than to messenger services.

In the context of the post, signal is much more vunerable than even basic things like email or web chats because police can effortlessly identify anyone in the group chat with a single request to cell company.

Signal can have a great interest in buying up private data linked with phone numbers and add people that they chat with with their phone numbers, sell again with the added data.

Just do like TOR services. Hash some garbage with your private key. done.

This is no excuse other than copying the leading app for no good reason.