I believe they have covered this question many times before, but I don’t see an answer on signal’s website. From memory, it had to do with not wanting to own the user’s contact list. Using a phone number allowed them to rely on a contact list on the users phone, which is not tied to the signal account. There was more nuance than that though.
> it had to do with not wanting to own the user’s contact list. Using a phone number allowed them to rely on a contact list on the users phone, which is not tied to the signal account.
That doesn't make any sense. Signal did the total opposite. It started keeping sensitive user data in the cloud including your name, your photo, your phone number, and a list of your contacts. It stores that data on their servers permanently.
Signal has always kept your name/pic/etc on their servers I believe, because otherwise you turn signal into a P2P application, which it is not. It's a fully encrypted application that stores minimal information. It is NOT P2P.
For example, your messages are stored on their servers until they're delivered.
If this is the first time you're hearing about the data collection, that should tell you everything you need to know about how trustworthy Signal is.
> Signal has always kept your name/pic/etc on their servers I believe
Wrong again I'm afraid. There really was a time when Signal didn't collect and store any user data on their servers. They've repeatedly bragged about times when governments have come around asking them for data and they were able to turn the feds away because that data was never collected in the first place. That changed with the update which added pins. Today, Signal now collects that very same data.
They store registered users phone numbers and allow discovery by making a request with a hashed version of the phone numbers on your contact list. They add an extra layer to allow attestation of the software doing this using Intel's secure enclave. They give many examples of responding to warrants with only whether the number has been registered and the timestamp of registration, which they explain is the only information they hold.
There's a horrible conflation of concepts here. A pretty big one.
When people talk about cloud services, they generally mean part of an application that runs on the cloud that participates as a trusted actor in the application's trust model.
What people in the linked thread are realizing is that "signal has a server" and they are confused because they thought signal didn't have a server, or something.
So, what's important about Signals servers is that, outside of initial key exchange which is verified by two parties out of band, they are not a trusted entity, ever. When you send a message it goes through signals servers. When you sync your profile picture with other devices, same thing. The data transits signals servers. This is made possible because of cryptography. By encrypting the data in a way that is indecipherable by 3rd parties (Signal's servers included) your data is isomorphic to random noise. So, the only thing Signal needs to do is route the random noise to the right place. If it doesn't do that, it's a denial of service and about the only attack you're vulnerable to if you use Signal. Otherwise, the receiver gets the exact random noise that you sent, but only they can make sense of it because of the miracle of cryptography.
If you're really doing to throw a fit because Signal syncs a profile picture between your devices using the same level of crypto as is used for messaging then you're honestly crazy.
No. Signal did not "not have a cloud" and now they "have a cloud". Not by any reasonable interpretation of the events.
Signal has a "cloud" a server where they collect and store your name, your phone number, your photo, and list of every person you've contacted using Signal. That data isn't some ephemeral encrypted string that is only present when you "sync your profile picture" or when you send a message. It is collected and stored on their server where it will sit for at least as long as you have an account.
The justification for it was so that you could get a new device and have Signal download all of your info from your Signal's server down to your device. The data collection first takes place as soon as you set a pin or opt out of setting one (at which point a pin is assigned for you automatically).
If you're a whistleblower or an activist, a list of every person you've been contacting using Signal is a highly sensitive data. No matter how you want to spin it, Signal is hosting that highly sensitive user data on their servers where Signal and 3rd parties alike could possibly gain access to them.
You should assume every bit of information sent on the internet is archived in a massive warehouse somewhere, because it is.
Thus, we have to trust the cryptography itself. Sending an encrypted message to a peer is no different from sending an encrypted message to yourself (other than the use of symmetric vs asymmetric crypto). The fact that you send a message to yourself which is stored persistently on signal's server doesn't change anything (and it's even opt in AFAIU). Sure, there are concerns about the implementation, but until someone can decrypt the blobs in storage (the crypto is broken) I don't see reason for outrage.
Pretty simply, if you don't trust the crypto then you have a very different threat model to pretty much everyone else. If you don't trust crypto you can't use the internet because you can't use TLS. You're relegated to networks where you trust every single node (where you don't need crypto) and other such stuff. Most of us trust the crypto because it's really the only practical option. I don't see the problem.
> You should assume every bit of information sent on the internet is archived in a massive warehouse somewhere, because it is.
Leaving aside the whataboutism here, you shouldn't assume that when you're using a secure messaging app that claims to be designed to never collect or store user data. Signal makes that claim at the start of their privacy policy and it is a lie. It started out true, but they begain colleting data and they refuse to update their policy.
> Thus, we have to trust the cryptography itself.
No one is suggesting we can't trust cryptography. The fact is that doesn't matter how strong your algprythm is when you're encrypting that data with a 4 digit number. You can 100% "trust the cryptography" and still acknollege that it won't take very long for someone to brute-force your pin and get your data plain text.
> Sending an encrypted message to a peer is no different from sending an encrypted message to yourself... (and it's even opt in AFAIU).
This has nothing to do with "sending data to yourself" and everything to do with Singal collecting data from you and storing it for itself. There is a massive difference between encrypting something yourself and sending that data to yourself and someone else copying data from you, encryping it, and saving it for themselves.
This data collection is also not opt in. At all. You can opt out of setting a pin, but if you do one will be automatically generated for you and your data still gets silently uploaded to Singal servers to be stored. The community spent months begging for Signal to add a way to opt out of this data collection, but they were ignored.
> Pretty simply, if you don't trust the crypto then you have a very different threat model
"The crypto" isn't the problem here. The problem is Signal collecting sensitive user data and permanently storing it on their servers in a manner that could allow it to be accessed by third parties and then not clearly disclosing that to their users and refusing to update their privacy policy to reflect the change.
Signal can't possibly read the data. How is that for itself? Only you can decrypt it! Signal doesn't have your data. They have garbage bits of effectively random noise.
You can prove it to yourself. Go take one of Signal's servers and try to find someone else's data there. You won't.
Why would Signal update their privacy policy to reflect the desire of misguided fear mongers? I certainly wouldn't do that if I were them.
They literally can. If you can brute force a 4 digit pin, you can access any of the data protected by a 4 digit pin.
Some pins are longer, but it's notable that even after a lot of backlash they continue to push for "pins" and not "passwords" knowing that many will continue to use a simple four digit number.
> You can prove it to yourself. Go take one of Signal's servers and try to find someone else's data there. You won't.
um... what?
> Why would Signal update their privacy policy
To accurately reflect the data they collect and how it is used? So that they don't lie to their users by making claims that are demonstrably false? To notify whistleblowers and activists that their information and the information of those who they are in contact with could be discovered by state actors who can force Signal to give them access? There's three good reasons right there.
I'm sorry you're so upset by this. I know the reality is uncomfortable but that doesn't make it "fear mongering". I honestly wish it wasn't true. I wish they weren't collecting user data, I wish they were doing more to secure what they do collect, and most of all I wish they were honest and forthcoming about what they are doing, but wishes can't change what is. I hope that regardless of if you use Signal or not, you'll try to accept facts even when they aren't easy to accept.
Let me make this clear: if the data is stored in a way that Signal's service cannot decipher it, then it's not collected by any reasonable definition of collected". In order for Signal to collect it they would have to obtain it, which they don't, and can't, do.
This term isn't just some loose word to be thrown around and abused on message boards. If we take your definition of collected where handling encrypted data is collecting it, then "the internet" collects all data. Uh oh.
What signal does is route encrypted messages between principals in a system. That's all they do. They don't collect personal information. Read their subpoena responses, they publish all of them.
> Let me make this clear: if the data is stored in a way that Signal's service cannot decipher it, then it's not collected by any reasonable definition of collected".
I think this is misguided, and confuses the truth. Data collected and stored remotely is being "collected and stored remotely" regardless of how well protected it is.
I will however concede that it is possible to design a system where data is encrypted on a device and then uploaded to the cloud in such a way that simply having that encrypted data on a remote server doesn't put that data at risk. Signal did not design their system in that way.
> If we take your definition of collected where handling encrypted data is collecting it, then "the internet" collects all data. Uh oh.
Again, this isn't about handling encrypted data - it's about the long term storage of highly sensitive but encrypted data - and as I said above, even that is fine if it's done correctly. Signal has done a poor job of designing their system which leaves user's data at risk.
> What signal does is route encrypted messages between principals in a system. That's all they do.
That used to be "all they do". Then, about two years ago they decided they wanted everyone to have profiles which would be kept on the cloud. As soon as you install the software, before you try to send any message to anyone you're asked to provide a pin to secure you data. Once you set one (or opt out of setting it yourself) it collects a bunch of data from your device (not needed for routing anything - remember you've just installed the app and are not trying to send or receive any message at this time) and having collected that data it encrypts it on your device using the pin, then it uploads that data to their cloud. That data can be recovered by you (or anyone else for that matter) by providing the pin that you set. The data they just collected and stored is not used to transmit, route, or delver messages. This data collection takes place in addition to any information needed temporarily to transmit, route, or delver messages.
> Read their subpoena responses, they publish all of them.
That's incorrect. They publish the ones they are allowed to publish under the law (look up "national security letters" for more info) and their refusal to provide one agency with data says nothing about the requests they are forced to comply with. Their favorite examples involve cases where Signal was unable to hand over the data because they didn't collect it in the first place. Today, because of changes in their data collection practices, they now collect exactly the kinds of data they were not collecting before and were therefore unable to provide.
It's unlikely that Signal would be compelled by a standard subpoena to brute force their users pins to access the encrypted data. It is far more likely that the data is already being collected by an agency on-site, and that the data collection is continuous and ongoing (look up "Room 641A" for an example of on-site data collection by the state).
The fact that it is unlikely that Signal would be compelled by a standard subpoena to brute force their users pins does not mean:
- Signal employees can't do it themselves any time they feel like it.
- State actors can't do it whenever they feel like it
- A hacker couldn't gain access to a server and do it
Because of the sensitive nature of the messages sent over the platform, and because they have explicitly marketed themselves to vulnerable groups like whistleblowers and activists it is critical that Signal be honest about the risks of using their software. They insist they don't collect any data, while in practice they do. They say they secure the data they have, in practice that data is exposed by way of multiple vulnerabilities that could very well endanger the freedom or even the lives of the people using Signal.
Can you link to the implementation? I'll agree that a 4 digit pin is rather egregious and trivially crackable. I don't know a single serious cryptographer that would allow such nonsense which is why your comment sounds so unbelievable. I thought they were blending the pin with some device-local entropy to make a reasonably strong key. I'd like to verify your claim.
Basically, they planned to get around much of the problem by depending on a very insecure secure enclave to make up for a lack of basic sound security practices.
They definitely do not encrypt your data with a 4 digit pin. They use Argon2 (a slow hash, not that it matters specifically here since the security depends largely on the entropy) to derive a 32-byte key. Then they derive subkeys: an auth key, and part of a final encryption key. The other part of the encryption key is 32-bytes of entropy. You store your entropy in an SGX enclave with a limited number of attempts allowed to combat the possibility of a weak pin.
Few things:
1. The vulnerabilities in question for SGX have been patched, only one of which affected Signal at all.
2. Signal preemptively combats any future speculative execution vulns by adding "don't speculate about this next branch" instructions before every single branch.
3. nit: SRV is a scheme to store the 256bits of entropy in the cloud, not the actual user data. It's unclear from those links whether Signal has actually deployed the "store encrypted contacts" portion.
4. It is concerning that the security of this entropy is tied to Intel's SGX implementation.
5. If you use a strong password, which security nuts would, none of this matters.
6. If you turn off your pin, none of this happens at all (so it's at least opt out but IIRC setting a pin was optional).
7. I don't find your interpretation particularly charitable to the truth of what's actually happened. It's incredibly reactionary.
I will give you:
1. The trust model for Signal has changed to include a dependence on a piece of Signal cloud to enforce a rate limit on (really access to) escrowed entropy IFF you use a weak pin.
2. There does seem to be unnecessary confusion surrounding this whole thing.
What bothers me reading through this is that it was never made clear to users that the security model would change if you enabled a weak pin, in other words that the strength of your pin/password is now important if you don't/can't/won't trust Signal+Intel. If that was made clear there would be no issues at all and concerned citizens would simply disable their pin and deal with the not-improved UX or choose a strong pin such that the entroy escrow SVR thing is entirely moot.
I don't think they need to update their privacy policy or user agreement to reflect these technical implementation details, though, as I've previously stated.
Moxie blames the poor reception on not having analytics. I'd say they should have known, it's pretty obvious you can't pretend you don't need a password and try to hide it from users if you want to add stuff that needs a password, like usernames. But I also know from first hand experience how difficult it is to just sit there and say "whelp, we can't build this thing that will make many users happy and make the product better because it isn't perfect".
What's sad is actually that this is all in service of enabling username messaging and dropping the phone number requirement which is exactly what everyone is yelling about. So it's like, they listen to feedback from people who want to use Signal without a phone number requirement. Then they build the thing that lets them take a crack at the nut. And then they get reamed by HN for having the audacity to try and build a secure solution to a problem that largely only exists on HN and only for Signal (nobody gives a shit that every other app under the sun just stores your contacts in plaintext). Must really suck to get that kind of response.
I'll probably go turn off my pin. I have no interest in signal managing my contacts.
I did oversimplify their encryption scheme, but the issue is that in the end you still only need a pin to get the unencrypted data. I agree that if they'd been honest about passwords and the need for a strong one this wouldn't be as big an issue. It's because they were not honest that I don't think it's fair to expect their users (even the security nuts) to do it. Their target demographic will include whistleblowers and journalists who aren't necessarily all that tech-savvy.
The strengths and weaknesses of SGX are debatable, I may lean on the pessimistic side, but as you say it impacts the security model of Signal users and to me that means they (and new users) should be clearly informed. The first line of their privacy policy says "Signal is designed to never collect or store any sensitive information." which is demonstrably false.
As for opting out, unless something has changed they still store your data on the cloud, it's just handled differently:
I don't know what options someone has after they've already created a pin, if there's a way to remove your data from the cloud, I stopped using signal before they forced the pin (back when you could still just ignore the notice) and getting real answers to these kinds of basic questions is way more difficult than it should be. This is, again, a service targeting very vulnerable people whose lives and freedom may be on the line.
I was one of those Signal users who wanted them to move away from requiring a phone number too. That said, what I was looking for was something more like Jami. They managed to create a system with usernames and passwords but without phone numbers or accounts keeping your data in the cloud.
I'm not shitting on Signal's efforts overall. A lot of great work went into Signal and I'm pissed I still haven't found a good replacement for it, but the changes they made hurt the security and safety of the people who depend on Signal. They are a massive intelligence target and I can't blame them for anything they were forced to do, and if their goal was to subtly drive people away by raising a bunch of red flags I thank them, but if this is their best effort at communication and building trust how charitable can they expect us to be when two years later so many of their users don't have a clear idea of what's being collected and stored or what that means for their safety?
>That doesn't make any sense. Signal did the total opposite. It started keeping sensitive user data in the cloud including your name, your photo, your phone number, and a list of your contacts. It stores that data on their servers permanently.
This is the first I've heard of that. And if it's true, it's a big problem.
Is there any documentation of this behavior that you can direct me to?
You aren't alone. There are a ton of people who have no idea Signal has been collecting and storing sensitive user data on their servers. There was a ton of discussion about it when the update rolled out and a lot of backlash from their users, which they ignored. They've since refused to update their privacy policy as well which I personally see as a canary warning users to avoid their service.
>You aren't alone. There are a ton of people who have no idea Signal has been collecting and storing sensitive user data on their servers. There was a ton of discussion about it when the update rolled out and a lot of backlash from their users, which they ignored. They've since refused to update their privacy policy as well which I personally see as a canary warning users to avoid their service.
Edit: This bit is apparently not the case. And more's the pity.
====Section affected by edit=========
I can't (and wouldn't try to) speak for anyone else, but if you disable the PIN functionality[0], Signal doesn't upload the information you're talking about.
==== End section affected by edit=========
Which isn't a new change (IIUC, PIN disablement was introduced ~2 years ago). I'd say that using the PIN functionality should be opt-in rather than opt-out, so in that respect I agree.
Further, Signal should probably update their policy documents to reflect the current state of affairs.
> I can't (and wouldn't try to) speak for anyone else, but if you disable the PIN functionality[0], Signal doesn't upload the information you're talking about.
This is also incorrect.
If you opt out of setting a pin, Signal creates a pin for you and uses that to encrypt the data it uploads to their servers. Again, not your fault. Signal has gone out of their way to avoid answering direct questions about this in a plain way.
This is absolutely NOT true. (1) Signal doesn't store your contacts, and (2) Signal only stores a name and a profile photo if you want, and in a secure wayhttps://signal.org/blog/signal-profiles-beta/
I'm sorry to be the one to tell you, but Signal 100% stores your contacts. They keep your name, your photo, your phone number, and a list of every person you've contacted using Signal. That data is permanently stored on their servers.
> "This should be updated for the recent changes where contacts are uploaded to Signal’s servers and stored permanently along with Groups V2 and other data, protected by a 4-digit minimum PIN and Intel SGX – there have been concerns 5 raised 2 in these forums, particularly if one of your contacts chooses a brute-forceable PIN which in the context of an Intel SGX vulnerability 1 could leak a lot of contact data if hacked, even if you choose a strong password."
See the two links sited in that comment for more information on why it isn't actually stored in "secure" way.
What would this list contain? You don't have a signal username. If you did you'd have to claim it somehow (degenerates to email or phone verification). It's not that simple.
Using phone numbers allows signal to plug into the existing state of the world and leverage it to upgrade the security of messaging for everyone who uses it. The one compromise is that it treats phone number as a short identifier (importantly, not cryptographic, it uses real crypto for that).
If you don't use phone numbers, your product would look more like Keybase. You have to somehow facilitate key exchange between people in a way that's actually usable. Otherwise all your security benefits go out the window because nobody uses your product. Signal understands this nuance perfectly which is why they're a successful product.
If I don't use Signal, then I'm not going to keep a list of my friends' Signal usernames on my phone.
If I subsequently sign-up for Signal, then I have no way to discover which of them use Signal - short of contacting them via some other method and asking for their Signal username, if any.
By making the Signal username the same as the user's phone number, I actually DO have a list of Signal 'usernames' on my phone already. As soon as I sign-up, I can send my list of friends' phone numbers to Signal and they can tell me which of those people have Signal accounts.
