The sad part is, that's what's keeping Signal safe from spam.
Also, average Joe is not using proxy to hide the IP-address of their device so they leak their identity to the server anyway. Signal is not keeping those logs so that helps.
Messaging apps cater to different needs, sometimes you need only content-privacy. It's not a secret you're married to your partner and you talk daily, but the topics of the conversation aren't public information.
When you need to hide who you are and who you talk to (say Russian dissident group, or sexual minorities in fundamentalist countries), you might want to use Tor-exclusive messaging tools like Cwtch. But that comes at a near-unavoidable issue of no offline-messaging, meaning you'll have to have a schedule when to meet online.
Signal's centralized architecture has upsides and downsides, but what matters ultimately is, (a) are you doing what you can in the architectural limitations of the platform (strong privacy-by-design provides more features at same security level), and (b), are you communicating the threat model to the users so they can make informed decision whether the applications fits their threat model.
If you intend to use SMS (phone numbers) as a resource constraint (sign up requires 'locking up' a resource that is worth at least a few cents) then at least you can offer a ZKP system where the 'consumed' phone number is not tied to an account. You could also offer to accept cryptocurrency for this function - call it a donation.
That Signal did none of those things implies that privacy was not their objective. Only secure communications was.
It's possible that the reason behind their anti-privacy stand is strategic, to discourage criminal use which could be used as a vector of attack against them. Doesn't change the fact that Signal is demonstrably anti-privacy by design.
> privacy was not their objective. Only secure communications was.
> Signal is demonstrably anti-privacy by design.
But your second is uncharitable and misses Signal's historical context.
The value of a phone number for spam prevention has been mentioned, but that's not the original reason why phone numbers were central to Signal. People forget that Signal was initially designed around using SMS as transport, as with Twitter.
Signal began as an SMS client for Android that transparently applied encryption on top of SMS messages when communicating with other Signal users. They added servers and IP backhaul as it grew. Then it got an iOS app, where 3rd party SMS clients aren't allowed. The two clients coexisted awkwardly for years, with Signal iOS as a pure modern messenger and Signal Android as a hybrid SMS client. Finally they ripped out SMS support. Still later they added usernames and communicating without exposing phone numbers to the other party.
You can reasonably disdain still having to expose a phone number to Signal, but calling it "anti-privacy by design" elides the origins of that design. It took a lot of refactoring to get out from under the initial design, just like Twitter in transcending the 140-character limit.
> You can reasonably disdain still having to expose a phone number to Signal, but calling it "anti-privacy by design" elides the origins of that design.
They introduced usernames without removing the requirement for phone numbers.
The parent attempted to excuse them by pointing out that the initial design was based on phone numbers. Putting aside the fact that initial design is irrelevant to present design criticism, they went out of their way to design usernames yet deliberately disallow signup without phone numbers.
> Not a very good case made since you obviously didn’t read the parent discussion.
This isn't an argument, do you have anything to back up your assertion?
If privacy wasn't their objective they would just have a database of all the phone numbers.
Perfect privacy would mean not sending any messages at all, because you can never prove the message is going to the intended recipient. Any actual system is going to have tradeoffs, calling Signal anti-privacy is not serious, especially when you're suggesting cryptocurrency as a solution.
A ZKP system where you make a public record of your zero-knowledge proof sounds anti-privacy to me. Even if you're using something obfuscated like Monero, it's still public. I see where you're coming from, but I think I would prefer Signal just keep a database of all their users and promise to try and keep it safe rather than rely on something like Monero.
They have exactly that. They rely on TPMs for "privacy" which is not serious.
> Perfect privacy would mean not sending any messages at all
Not sending messages is incompatible with secure messaging which is the subject of the discussion...
> ZKP system where you make a public record of your zero-knowledge proof sounds anti-privacy to me.
A zero-knowledge proof provably contains zero information. Even if you use a type of ZKP vulnerable to a potential CRQC it's still zero information and can never be cracked to reveal information (a CRQC could forge proofs however).
> especially when you're suggesting cryptocurrency as a solution
Would you elaborate on why cryptocurrencies are not a solution? Especially if combined with ZKPs to sever the connection between the payment and the account. When combined with ZKPs, they could even accept Paypal for donations in exchange for private accounts.
It's also possible that a lot of the criticism for Signal setting a practical/realistic level of what security they will try to provide, is from people who would rather that people either
1. were unable to communicate effectively, or
2. used no security at all.
Do you really use a communication system where you have all exchanged private keys in person and where even the fact that you use it is hidden from your government and phone operator?
If you wanted to keep it safe from spam, you'd use a proof-of-work scheme using a memory-hard hash function like scrypt, or a Captcha, or an invite-code system like lobste.rs or early Gmail. Signal's architects already knew that when they started designng it.
>proof-of-work scheme using a memory-hard hash function like scrypt
So who's doing the computation? The spammer can't afford to run 3 second key derivation time per spam device? Or how long do you think normal user will wait while you burn their battery power before saying "Screw it, I'll just use WA"? Or is this something the server should be doing?
>Captcha
LLMs are getting quite good at getting around captchas.
>invite-code system
That works in lobste.rs when everyone can talk together, and recruit interesting people to join the public conversation. Try doing that with limited invites to recruit your peers to build a useful local network of peers and relatives. "I'm sorry Adam, I'm out of invites can you invite my mom's step-cousin, my mom needs to talk to them?"
>Signal's architects already knew that when they started designng it.
I think they really did, and they did what the industry had already established as the best practice for a hard problem.
The only reasonable alternative would've been email with heavy temp-mail hardening, or looking into the opposite end of Zooko's triangle and having long, random, hard-to-enumerate usernames like Cwtch and other Tor-based messengers do. But even that's not removing the spam-list problem of any publicly listed address ending up in a list that gets spammed with contact requests or opening messages with spam.
Those are reasonable questions, but they suggest that you don't understand the landscape very well.
The user's device has to do the computation for it to be effective. How long does it normally take to sign up for a new messaging service like WhatsApp? Five minutes? You should burn the user's cellphone battery for about half that long, 150 seconds, 50 times more than you were thinking. Plus another half-minute every time you add a new contact. Times two for every time someone blocks you, up to a limit of 150 seconds. Minus one second for each day you've been signed up. Or something like that.
The value of signing up for Signal is much higher to a real user than it is to a spammer, so you just have to put the signup cost somewhere in the wide range in between.
LLMs didn't exist when Signal was designed, and Captchas still seem to be getting a lot of use today.
Invite codes worked fine for Gmail, and would work even better for any kind of closed messaging system like Signal; people who don't know any users of a particular messaging system almost never try to use it. The diameter of the world's social graph is maybe ten or twelve, so invite codes can cover the world's social graph with only small, transitory "out of invites" problems.
The "industry" had "established" that they "should" gather as much PII as possible in order to sell ads and get investments from In-Q-Tel.
> How long does it normally take to sign up for a new messaging service like WhatsApp? Five minutes? You should burn the user's cellphone battery for about half that long, 150 seconds
If you actually do that you're going to crash a lot of cellphones and people will rightly blame your app for being badly coded.
What, their CPUs will overheat? I've run infinite loops on cellphones lots of times without that happening. In fact, I'm running four of them right now, and have been for the last five minutes as I write this comment. The battery drain is annoying but I haven't seen instability. I've run plenty of compiles on cellphones (things like BLAS and Numpy) that take longer than that, and I've never seen one crash a phone.
>but they suggest that you don't understand the landscape very well.
Yeah, what could I possibly know about secure messaging.
>Plus another half-minute every time you add a new contact.
Can you point to some instant messaging app that has you wait 30 seconds before talking to them? Now niché is it?
You want proper uptake and accessibility to everyone, you need something like Samsung A16 to run the work in 150 seconds. Some non-amateur spammer throws ten RTX 5090s to unlock access to random accounts at 80x parallelism (capped by memory cost), with the reasonable time cost of whatever iterations that is, with quite a bit shorter time than 150 seconds. 121.5GFLOPs vs 10x104.8 TFLOPs leads to overall performance difference of 8,800x. And that account is then free to spam at decent pace for a long time before it gets flagged and removed.
The accounts are not generated in five minutes per random sweat shop worker: https://www.youtube.com/watch?v=CHU4kWQY3E8 has tap actions synced across sixty devices. And that's just to deal with human-like captchas that need to show human-like randomness. Proof-of-work is not a captcha, so you can automate it. Signal's client is open source for myriad of reasons, the most pressing of which is verifiable cryptographic implementations. So you can just patch your copy of the source to dump the challenge and forward it to the brute force rig.
Either the enumeration itself has to be computationally infeasible, or it has to be seriously cost limited (one registration per 5 dollar prepaid SIM or whatever).
>Invite codes worked fine for Gmail
Yeah and back in ~2004 when Hotmail had 2MB of free storage, GMail's 1,000MB of free storage may have also "helped".
If the PoW cost is a low-end cellphone CPU for 2.5 minutes, then it's nothing to the spammer with the 200-core hourly AWS server. If each spammer can create 10000 identities (not connections, identities) per hour, then you might as well not have a limit at all. If they could even create only 2 identities per day that would be enough to spam with (yet still unacceptable to actual users). 250000 identities per day is way too many.
The speed ratio is much smaller than you say with memory-hard PoW problems, which depend on the amount of RAM you have (and its response time). But it's surely true that a spammer could create many accounts per day, perhaps 1000 per hour on a big server, which could then go on to spam a few accounts each before becoming uneconomical to keep using.
But that would still put the CPM of the spam around US$2, which very few spammers can afford. Maybe mesothelioma lawyers and spearphishers.
You don't have to make spamming physically impossible, just unprofitable.
Invite codes worked fine for Gmail, but you weren't limited to only the people on Gmail to talk to. It was a full, regular email service. You could email anyone and receive mail from anyone. I doubt it would have been very successful if it was invite only and you could only email other Gmail users for the first few years.
Waze was also invite-only, G+ was initially invite only. Did that model help or hurt them?
I think it helped them. Gmail had more trouble with invite codes because some people wanted a Gmail account, but didn't know any existing Gmail users, because Gmail was useful for communication with non-Gmail users.
G+ didn't have that problem so much, but I don't remember it using invite codes.
There are people who believe that proof-of-work isn't very effective, but none of them have succeeded in spamming the Bitcoin network with blocks they've mined, driving the other miners out of business, nor (for the last several years) with spamming the Bitcoin network with dust transactions they've signed, so I don't think we should take their opinions very seriously.
Bots may be better than humans at Captchas now, although I'm not certain of that, but they certainly weren't when Signal was designed.
I don't see why invite codes would be a problem for mainstream use.
> There are people who believe that proof-of-work isn't very effective, but none of them have succeeded in spamming the Bitcoin network with blocks they've mined, driving the other miners out of business, nor (for the last several years) with spamming the Bitcoin network with dust transactions they've signed, so I don't think we should take their opinions very seriously.
Different system. The parent and GP are talking about proof-of-work being used directly for account creation. If a chat service required mining-levels of PoW (and hence any prospective new users to have an ASIC), it would not be very popular. Nor would it be very popular if it used a relative difficulty system and the spammers used dedicated servers while the legitimate users had to compete using only their phones.
> none of them have succeeded in spamming the Bitcoin network with blocks they've mined
I'm not saying you're wrong, but I have no idea what you're getting at, because the sentence sounds kind of absurd. As a result, I'm not sure if it addresses your point, but just to throw it out there: Bitcoin and anti-spam are different applications of proof of work. Anti-spam has to strike a compromise between being cheap for the user (who is often on relatively low-powered mobile hardware), and yet annoying enough to deter the spammer. It's not unreasonable to believe that such a compromise does not exist.
> Bots may be better than humans at Captchas now, although I'm not certain of that, but they certainly weren't when Signal was designed.
Fair point, but again, even in 2014, an instant messenger with captchas would have much more friction than every other messenger. And captchas aren't just bad because they introduce enough friction to drive away pretty much everybody: they also make users feel like they're being treated as potential criminals.
> I don't see why invite codes would be a problem for mainstream use.
Can you elaborate? Invite codes blocking access to the service itself "like lobste.rs" mean that no one can use your service unless they've been transitively blessed by you. That's obviously going to limit its reach...
Bitcoin had a spam transaction problem ("dust transactions") which was a bigger problem than email spam, because every transaction is received by every node. It was easy to solve because Bitcoins are minted by proof of work.
I don't think a Captcha for signup would have been much friction. Certainly less than providing a phone number.
Why would someone want to use a closed messaging service like Signal unless they knew an existing user? I don't think that the requirement for that existing user to invite them would be a significant barrier. So I think it's not going to limit its reach.
Signal blasted my whole contacts list the day I signed up so that I was surprised to see lots of people saying "finally you got signal". That was also the moment I uninstalled the app. Leaking contact info appears to be part of the design.
Should have deleted my account instead of just removing the app, because it turns out the difference between using signal and using SMS is obscured for most phones, and when people thought they were texting me they weren't. I was just out of contact for a long time as people kept sending me the wrong kind of messages. I suppose one could argue protecting contact/identity is not a real goal for e2e encryption, but what I see is a "privacy oriented" service that's clearly way too interested in bootstrapping a user base with network effects and shouldn't be trusted.
> Those people already had your contact info, probably.
What leaked was that I was a signal user, and that the person on the other side was a signal user. The security implications are obvious, and by itself, that's already enough to get someone who really needs to care about privacy killed.
> Also, I think there is a setting in Signal to prevent that
False. It happened without my permission as soon as the app was installed, and there was no way to opt out. Maybe they changed it since then, but the fact remains they obviously cared more about network-effects and user-counts than user privacy.
Sigh, there's just no need for this kind of apologism. You could just admit that a) it's bad behavior, b) they did it on purpose, and c) it's not possible to trust someone who does something like this. I'm aware they are nonprofit, so I don't know why it's like this, but the answer is probably somewhere in the list of donors.
How would you suggest Signal allow you to communicate with your contacts without leaking the fact that both of you are Signal users? Should it just blackhole the message if the other number doesn't have an account?
I understand the unease about the notifications, but there are some hard tradeoffs between how you can store as little information as possible, remain as decentralized as possible, while getting the same benefits as centralized systems like Facebook.
I'm really of the opinion that a messenger similar to Signal but more centralized in the fashion of WhatsApp or even Facebook Messenger should exist, but I also understand why Signal works the way it does.
Suggestion: it should, at very least, not show a UI a notification "_ is now on signal!" As a nice to have, yes, it should blackhole a message until at least one reply happens.
Yeah, no. The whole "every perspective has some validity" thing won't really apply to most safety/security issues. The most charitable thing to say here is that the workflow is completely broken. Less charitable but also valid is pointing out that it's actively harmful, and deliberate. I would be really surprised if this hadn't ever caused serious consequences whether a whistle blower was fired, an abused spouse got extra abused, or an informant was killed. If you think you've got a "valid perspective" that prioritizes mere user-discovery over user-safety, then you should not be attempting work that's close to safety and security, full stop.
> What leaked was that I was a signal user, and that the person on the other side was a signal user.
Clearly, either this was before Signal had its username-lookup-only feature, or you opted into letting people find you by your phone number. At that point, the information is already effectively leaked in the same way (it’s easy for anyone to enumerate all phone numbers, let alone for you to enumerate your own contacts or vice versa), and if the notification surprised you then the absence of the notification would simply have been giving you a false sense of security.
Communication by non-phone-number identifiers is critically important, and I’m glad for recent Signal developments in that direction and hopeful for more in the future, but opting into phone-number-based communication and complaining that your contacts were merely notified about the communication option they would have been able to access anyway on a security or privacy basis is silly. The fact that this information (your contacts) passes through Signal is much more objectionable to me, even though they do the SGX thing, and I would never recommend allowing it access to your contacts for that reason.
When someone on your contacts list gets Signal, Signal displays this in its UI. I don't think this is a privacy violation. Signal aims to hide your messages, but it does not have its own contacts system, and piggybacks on your existing phone number and phone number contacts. Nor does it attempt to hide the fact you have Signal.
The people that already had your contact info in their devices were notified that you joined Signal via that contact info?
Seems like it was working as designed, if you don't want any app to get your contact info don't share your contact info to anyone ever. Eventually they will share that info with any app.
Security and usability are frequently at odds. The ease with which users can discover and exchange messages with their contacts is a major usability issue. Phone number as a proxy for identity mostly works, at the cost of some privacy risks.
This made sense when Signal/TextSecure allowed users to send regular SMS, making it easy to convince others to set it as their default messenger.
Now that this crucial adoption feature has been removed, it makes zero sense for Signal to continue to rely on phone numbers. Since that feature has been removed, the utility of Signal has been lost anyway and many in my groups returned to regular SMS. So the system is already compromised from that perspective. At least forks such as Session tried to solve this (too bad Session removed forward secrecy and became useless)
I agree, but since a messaging apps utility is some fraction of the square of the # of users on the platform, a facile way to propagate virally is a de facto requirement for an app targeting wide spread adoption / discovery rather than targeted cells of individuals focused around a pre shared idea.
It’s a compromise meant to propagate the network, and it has a high degree of utility to most users. There are also plenty of apps that are de-facto anonymous and private. Signal is de facto non-anonymous but private, though using a personally identifiable token is not a hard requirement and is trivial to avoid. (A phone number of some kind is needed once for registration only)
There's no alternative to reduce spam and fake accounts, unless we collectively are fine with blocking Russia, India, China, and friends from the internet.
Also, average Joe is not using proxy to hide the IP-address of their device so they leak their identity to the server anyway. Signal is not keeping those logs so that helps.
Messaging apps cater to different needs, sometimes you need only content-privacy. It's not a secret you're married to your partner and you talk daily, but the topics of the conversation aren't public information.
When you need to hide who you are and who you talk to (say Russian dissident group, or sexual minorities in fundamentalist countries), you might want to use Tor-exclusive messaging tools like Cwtch. But that comes at a near-unavoidable issue of no offline-messaging, meaning you'll have to have a schedule when to meet online.
Signal's centralized architecture has upsides and downsides, but what matters ultimately is, (a) are you doing what you can in the architectural limitations of the platform (strong privacy-by-design provides more features at same security level), and (b), are you communicating the threat model to the users so they can make informed decision whether the applications fits their threat model.