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Comment by ddtaylor

1 day ago

I don't know signal very well but when I have spoken to others about it they mention that the phone number is the only metadata they will have access to.

This seems like a good example of that being enough metadata to be a big problem.

I've been hearing for years people say "Signal requires phone number therefore I don't use it", and I've been hearing them mocked for years.

Turns out they were right.

  • They weren't though? Signal requires a phone number to sign up and it is linked to your account but your phone number is not used in the under the hood account or device identification, it is not shared by default, your number can be entirely removed from contact disovery if you wish, and even if they got a warrant or were tapping signal infra directly, it'd be extremely non trivial to extract user phone numbers.

    https://signal.org/blog/phone-number-privacy-usernames/

    https://signal.org/blog/sealed-sender/

    https://signal.org/blog/private-contact-discovery/

    https://signal.org/blog/building-faster-oram/

    https://signal.org/blog/signal-private-group-system/

    • In past instances where Signal has complied with warrants, such as the 2021 and 2024 Santa Clara County cases, the records they provided included phone numbers to identify the specific accounts for which data was available. This was necessary to specify which requested accounts (identified by phone numbers in the warrants) had associated metadata, such as account creation timestamps and last connection dates.

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    • Which of those links actually say that your phone number is private from Signal? If anything, this passage makes it sound like it's the reverse, because they specifically call out usernames not being stored in plaintext, but not phone numbers.

      >We have also worked to ensure that keeping your phone number private from the people you speak with doesn’t necessitate giving more personal information to Signal. Your username is not stored in plaintext, meaning that Signal cannot easily see or produce the usernames of given accounts.

  • Signal's use of phone numbers is the least of your issues if you've reached this level of inspection. Signal could be the most pristine perfect thing in the world, and the traffic from the rest of your phone is exactly as exposing as your phone number is when your enemy is the US government who can force cooperation from the infrastructure providers.

    • Your point is correct but irrelevant to this conversation.

      The question here is NOT "if Signal didn't leak your phone number could you still get screwed?" Of course you could, no one is disputing that.

      The question is "if you did everything else perfect, but use Signal could the phone number be used to screw you?" The answer is ALSO of course, but the reason why we're talking about it is that this point was made to the creator of Signal many many times over the years, and he dismissed it and his fanboys ridiculed it.

  • I talked to Moxie about this 20 years ago at DefCon and he shrugged his shoulders and said "well... it's better than the alternative." He has a point. Signal is probably better than Facebook Messenger or SMS. Maybe there's a market for something better.

    • Is there any reason they didn't use email? It seems like something that would have been easier to keep some anonymity., while still allowing the person to authenticate.

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    • I remember listening to his talks and had some respect for him. He could defeat any argument about any perceived security regarding any facet of tech. Not so much any more. He knows as well as I do anything on a phone can never be secure. I get why he did it. That little boat needed an upgrade and I would do it too. Of course this topic evokes some serious psychological responses in most people. Wait for it.

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  • Suppose they didn't require that. Wouldn't that open themselves up to DDoS? An angry nation or ransom-seeker could direct bots to create accounts and stuff them with noise.

    • I think the deal is you marry the strong crypto with a human mediated security process which provides high confidence the message sender maps to the human you think they are. And even if they are, they could be a narc. Nothing in strong crypto prevents narcs in whom ill-advised trust has been granted from copying messages they're getting over the encrypted channel and forwarding them to the man.

      And even then, a trusted participant could not understand they're not supposed to give their private keys out or could be rubber-hosed into revealing their key pin. All sorts of ways to subvert "secure" messaging besides breaking the crypto.

      I guess what I'm saying is "Strong cryptography is required, but not sufficient to ensure secure messaging."

    • Yes. Cheap–identity systems such as Session and SimpleX are trivially vulnerable to this, and your only defence is to not give out your address as they are unguessable. If you have someone's address, you can spam them, and they can't stop it except by deleting the app or resetting to a new address and losing all their contacts.

      SimpleX does better than Session because the address used to add new contacts is different from the address used with any existing contact and is independently revocable. But if that address is out there, you can receive a full queue of spam contacts before you next open the SimpleX app.

      Both Session and SimpleX are trivially vulnerable to storage DoS as well.

    • There are a lot of solutions to denial of service attacks than to collect personal information. Plus, you know, you can always delete an account later? If what Signal says is true, then this amounts to a few records in their database which isn't cause for concern IMO

The steps to trouble:

- identify who owns the number

- compel that person to give unlocked phone

- government can read messages of _all_ people in group chat not just that person

Corollary:

Disappearing messages severely limits what can be read

  • Unless they compel people at gunpoint (which prevents the government from bringing a case), they will probably not have much luck with this. As soon as a user sets up a passcode or other lock on their phone, it is beyond the ability of even most parts of the US government to look inside.

    It's much more likely that the government convinces one member of the group chat to turn on the other members and give up their phone numbers.

    • > which prevents the government from bringing a case

      Genuinely, from outside, it seems like your government doesn't give a damn on what they are and aren't allowed to do.

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    • They'll just threaten to throw the book at you if you don't unlock your phone, and if you aren't rich, your lawyer will tell you to take the plea deal they offer because it beats sitting in prison until you die.

    • All they have to do is pretend to be a concerned neighbor who wants to help give mutual aid and hope that someone in the group chat takes the bait and adds them in. No further convincing is needed.

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    • If you aren't saving people's phone numbers in your own contacts, signal isn't storing them in group chats (and even if you are, it doesn't say which number, just that you have a contact with them).

      Signal doesn't share numbers by default and hasn't for a few years now. And you can toggle a setting to remove your number from contact discovery/lookup entirely if you are so inclined.

    • > it is beyond the ability of even most parts of the US government to look inside.

      I'm sure the Israeli spyware companies can help with that.

      Although then they'd have to start burning their zero days to just go after protestors, which I doubt they're willing to do. I imagine they like to save those for bigger targets.

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    • There are multiple companies that can get different amounts of information off of locked phones including iPhones, and they work with LE.

      I’m also curious what they could get off of cloud backups. Thinking in terms of auth, keys, etc. For SMS it’s almost as good as phone access, but I am not sure for apps.

    • I'm confident the people executing non-complaint people in the street would be capable of compelling a citizen.

    • Which is just a redux of what I find myself saying constantly: privacy usually isn't even the problem. The problem is the people kicking in your door.

      If you're willing to kick in doors to suppress legal rights, then having accurate information isn't necessary at all.

      If your resistance plan is to chat about stuff privately, then by definition you're also not doing much resisting to you know, the door kicking.

  • It's even easier than that. They're simply asking on neighborhood Facebook (and other services too, I assume) groups to be added to mutual aid Signal groups and hoping that somebody will add them without bothering to vet them first.

  • I think disappearing messages only works if you activate it on your local device. And if the man compromises someone without everyone else knowing, they get all messages after that.

    But yes... it does limit what can be read. My point is it's not perfect.

  • compel that person to give unlocked phone

    Celebrite or just JTAG over bluetooth or USB. It's always been a thing but legally they are not supposed to use it. Of course laws after the NSA debacle are always followed. Pinky promise.

Presumably this is data taken from interdicted phones of people in the groups, not, like, a traffic-analytic attack on Signal itself.

  • It appears to be primarily getting agents into the chats. To me the questionable conduct is their NPSM-7-adjacent redefining of legal political categories and activities as "terrorists/-ism" for the purpose of legal harassment or worse. Whether that is technically legal or not it should be outrageous to the public.

  • I wonder whether the protesters could opt for offshore alternatives that don't require exposing their phone number to a company that could be compelled to reveal it by US law. For example, there is Threema[1], a Swiss option priced at 5 euros one-time. It is interesting on Android as you can pay anonymously[2], therefore it doesn't depend on Google Play and its services (they offer Threema Push services of their own.) If your threat model includes traffic analysis, likely none of it would make much difference as far as US state-side sigint product line is concerned, but with Threema a determined party might as well get a chance! Arguably, the US protest organisers must be prepared for the situation to escalate, and adjust their security model accordingly: GrapheneOS, Mullvad subscription with DAITA countermeasures, Threema for Android, pay for everything with Monero?

    [1] https://threema.com/

    [2] https://shop.threema.ch/en

    • It's worth noting that the way Signal's architecture is set up, Signal the organisation doesn't have access to users' phone numbers.

      They technically have logs from when verification happens (as that goes through an SMS verification service) but that just documents that you have an account/when you registered. And it's unclear whether those records are available anymore since no warrants have been issued since they moved to the new username system.

      And the actual profile and contact discovery infra is all designed to be actively hostile to snooping on identifiable information even with hardware access (requiring compromise of secure enclaves + multiple levels of obfuscation and cryptographic anti-extraction techniques on top).

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I don't think it's much of a problem at all. Many of the protesters and observers are not hiding their identities, so finding their phone number isn't a problem. Even with content, coordinating legal activities isn't a problem either.

  • I would never agree with you. protestors behaving legally or practicing civil disobedience can still have their lives ruined by people in power.

    https://www.phoenixnewtimes.com/news/arizona-supreme-court-s...

    • > protestors behaving legally or practicing civil disobedience can still have their lives ruined by people in power.

      They surely can. But the point was more than the people in power don't really need Signal metadata to do that. On the lists of security concerns modern protestors need to be worrying about, Signal really just isn't very high.

    • This is the price we pay to defend our rights. I would also expect any reasonable grand jury to reject such charges given how flagrantly the government has attempted to bias the public against protesters.

  • conspiracy charges are a thing, and they'll only need a few examples of manifestly illegal interference.

    it will be quite easy for a prosecutor to charge lots of these people.

    it's been done for less, and even if the case is thrown out it can drag on for years and involve jail time before any conviction.

    • If they could arrest people for what they've been doing, they would have already arrested people. And they have arrested a few here and there for "assault" (things like daring to react when being shoved by an annoyed officer), but the thing that's really pissing DHS off is that the protesters and observers are not breaking the law.

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    • Conspiracy requires an agreement to commit an illegal act, and entering into that agreement must be intentional.

  • Some of the signal messages I've seen screenshotted (granted screenshots can be altered) make it seem like the participants have access to some sort of ALPR data to track vehicles that they think are ICE. That would probably be an illegal use of that data if true.

    • > make it seem like the participants have access to some sort of ALPR data to track vehicles

      The whole reason cops love ALPR data is anyone's allowed to collect it, so they don't need a warrant.

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  • Government intimidation of the practice of constitutional rights... what ever could go wrong.

    • I was replying specifically to this:

      > This seems like a good example of that being enough metadata to be a big problem

      I was not saying it's not a problem that the feds are doing this, because that's not what I was replying to.

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    • That seems like a weak argument.

      I mean, carrying a weapon is a 2nd amendment right, but if I bring it to a protest and then start intimidating people with it, the police going after me is not "Government intimidation of the practice of constitutional rights".

      Protesting is a constitution right, but if you break the law while protesting, you're fair game for prosecution.

Was starting to think about setting up a neighborhood Signal group, but now thinking that maybe something like Briar might be safer... only problem is that Briar only works on Android which is going to exclude a lot of iPhone users.

  • I spent a dozen years in SF, where my friend circles routinely used Signal. It's my primary messaging app, including to family and childhood friends.

    I live in NY now. Just today, I got a message from a close friend who also did SF->NY "I'm deleting Signal to get more space on my phone, because nobody here uses it. Find me on WhatsApp or SMS."

    To a naïve audience, Signal can have a stigma "I don't do anything illegal, so why should I bother maintaining yet-another messenger whose core competency is private messaging?" Signal is reasonably mainstream, and there are still a lot of people who won't use it.

    I suspect you'll have an uphill battle using something even more obscure.

    • > Signal can have a stigma "I don't do anything illegal, so why should I bother ..."

      Aside: I see similar attitudes when I mention I use VPN all of the time

  • Why wouldn't you just use random abandoned forums or web article message threads? Iirc this is what teenagers used to do when schools banned various social media but not devices. Just put the URL in a discrete qr code that only a person in the neighborhood could see.