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Comment by kube-system | Hacker News Reader

Isn’t a bit of a privacy flaw that signal exposes who uses the app by phone number?

Well, certainly an anonymity flaw. Privacy is different than anonymity. Signal does not purport to provide anonymity. Anyone on the system can check for any other user by knowing their phone number. That tends to be the cost of the convenience of the automatic contact discovery provided by phone based messengers like Signal.

Anonymous messaging is an entire category by itself. It is a much more difficult problem. Fortunately, most people don't need anonymity, most of the time. I really don't care who knows that I am communicating with friends, family or the people related to my business. If anything, I care less that someone might find out I use Signal. If I encounter a situation where I need to be anonymous I can and will have to take special measures for a while. Temporary anonymity is relatively easy. The identity management is a cinch.

It is. Its also a security issue - Phone numbers aren't unique. It was interesting seeing signal say my deceased father was 'on signal', it's just the same number recycled to someone else.

I think unique has a specific meaning in your context which isn't what the standard definition of unique means. There are never two people in a carrier's database assigned to the same number. It can however be assigned to another person as long as it is deassigned from the previous person. The number, at any point, is always unique.

Privacy flaw and a security flaw: it is feasible to take over somebody's phone number through social engineering attack on the phone co's tech support. The tech support has ability to issue replacement SIM cards for users, and if an attacker socially engineers them to send SIM card with your number to them, it's a game over for you.

That is aside of the obvious problem of phone numbers being recycled for re-issue after having been abandoned for a stretch of time.

Not exactly a security flaw, as the new owner of the phone number won't have the original owner's secret keys (they never leave the phone, of course) and Signal will still send the messages to the previously authenticated client.

Taking over a Signal account requires access to the phone number and the password used to register it (or waiting a week). And this will still not give the attacker access to the private keys; When these keys change, Signal will put an alert message on ongoing chats and ask for confirmation.

It gets really interesting when you don't allow apps to see your contacts. Take Clubhouse for example, I never allowed it to see my contacts but it does show me all the people who have leaked my personal info to the app because it's made them auto follow me.

So yeah cool I can see that my boss, 4 ex-coworkers, my ex-bosses ex-wife, and I think a recruiter have all leaked my personal info to Clubhouse.

For a normal consumer it's not a flaw. But if you are a journalist or in any profession where sharing number is a big NO then yes it's not a good design.

Case 1: me and my friend want to communicate on signal. If he messages me on Signal there won't be any way to know if that's actually him. I would have to call him and confirm if its really him. For a tech-savvy person who is like crazy about privacy this is not a big deal. But for a normal consumer this make them remove the signal.

Case 2: You want to message someone who you already communicate via WhatsApp or calls on signal. Again from an average consumer point. Calling them and asking them for their signal ID is again inconvenient. Imagine doing this for 400 contacts if you try to move from WhatsApp to signal.

There are other secure messaging app which doesn't require number or even email. But then again, you meet the person or call him and then get his id.

Not sharing mobile number is really for few selected cases and those people form a very small percentage of the market.

Having a feature similar to telegram where you share your number with selected people. Or have a disposal ID which can be used to start a chat and then dispose that ID so that it can'be used again or linked to your account. Something like this would make more sense and probably serve that small percentage of people as well. An ID which gets destroyed once it's used to make a connection. One time use ID only. This is a good way as well. Secret chats which stays on one device only, or you need separate credential for.

I should be able to make a sample app like this. It can be a good demo project.

  yes. That is the point.

Well its a tradeoff to get the instant social network of your phonebook.

signal is not without its shortcomings

There was a recent issue where Chinese citizens pointed out that IMEs with telemetry enabled could capture what you type into Signal and it didn't warn you or try to mitigate this; the Signal guy ignored them, then dodged them for weeks and told everyone they were harassing him, then a white guy pointed out the same thing and his suggestions were immediately taken up.

And what was the suggestion? The flow of information is (You typing → IME converts key presses into text → Signal receives text) so Signal can't do anything to prevent a malicious IME from sending the text elsewhere. The best they could do is raise users' awareness that Signal won't protect them if there's spyware with privileged access on their device, and that their IME might be such spyware.

Mainly the OS has security options to prevent IME network connections that aren't always on by default, but users can enable them. (They might be off because it disables some features that need internet access.)

IIRC there was also some Android API that could be used in the app to help, but I don't remember what it actually did atm.

Perhaps your man the incognito keyboard option? Signal uses it, but no API I can imagine will protect against a malicious IME.

Worse still, even if you block IME internet access on a device with a factory-maliciois IME, they could just upload the data using some other service on the device.

Installing a known-good IME seems like the only fix I can think of?

If I remember correctly the claim was from a Chinese citizen who pointed this out and when Signal didn't treat this as a major security issue (which I felt was understandable given that her concern was mostly along the lines of "you can't say that Signal is secure given that people install other software on their phone that could be a keylogger so you should have a disclaimer") she decided to continue to escalate on social media until she was, IMO, harassing Moxie for his "lack of engagement". I didn't come away particularly impressed by that exchange.

Exactly, this had nothing to do with one person being Chinese and the other being white.

How so? I don't find it violating in any way that someone knows that I'm using a messenging app due to my phone number. They aren't exactly private in the first place.

It would be the same if there were usernames, although those would be far harder to assign to a person. Thankfully, Signal is working on that feature and hopefully it's released soon. I'd like to one day not have any phone number at all. It's a system that feels very much antiquated...

https://app.wire.com already has that feature and it is based on signal protocol.

Has it been audited by external, independent security researchers?

Yes, it's open source and anyone can look at the source code instead of appealing to authority.

That's not what I asked. Generally laypeople are not going to be good judges of whether or not an encryption protocol is sufficiently secure.

Has it been audited by security researchers?

You're assuming it takes considerable skill to fuzz an algorithm or look for back doors and easter eggs? To answer your question, I don't know if Wire's been audited by paid researchers. I personally prefer a customer-exposed product whose each commit you can look up rather than the remote promise of security in a locked and hidden program.

Why can't it be both?

Bitwarden is open-source (both the server and clients) AND has been independently audited for a security review.

> You're assuming it takes considerable skill to fuzz an algorithm or look for back doors and easter eggs?

This is usually a good assumption.

It is not impossible to create code which looks like it does one thing while simultaneously doing ya-mother.

http://underhanded-c.org/

"look" is a weak word. Anyone with eyes can look.

https://wire.com/en/security/#audits

Yes, with published reports, but it looks like they haven't published new ones in a few years.

Wire uses MLS [1], it has nothing to do with the Signal protocol.

[1]: https://messaginglayersecurity.rocks/

afaik Wire works on MLS like many others do - but according to Wikipedia Wire uses the Signal Protocol. Your "source" does not back up your claim

I just read the Wikipedia page and it says, emphasis mine:

> Wire's instant messages are encrypted with Proteus, a protocol that Wire Swiss developed based on the Signal Protocol.

That doesn't sound like "Wire uses the Signal Protocol" to me.

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