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If people in Iran could find themselves in trouble for using Signal I'd strongly advise they avoid it and look for some other solution.

Ever since Signal started collecting and permanently storing sensitive user data in the cloud (your name, photo, number, a list of everyone you contact using Signal) it's become much more dangerous for people who want to protect themselves and the people they are in contact with. Because Signal insists on keeping your contacts in the cloud it's possible in some cases for someone to collect a list of your contacts simply by brute forcing a 4 digit pin.

It would be horrible to end up in trouble or see your friends and family hurt because Signal wasn't forthcoming about the fact that they were collecting your info and keeping it on their servers.

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> Ever since Signal started collecting and permanently storing sensitive user data in the cloud (your name, photo, number, a list of everyone you contact using Signal)

None of this FUD is true. None of the information you listed is collected or stored by Signal. You can verify this yourself by looking at the various government warrants and subpoenas, and Signal's responses: https://signal.org/bigbrother/

> None of the information you listed is collected or stored by Signal.

That's a lie. I don't blame you for not knowing the truth though, Signal has gone to some trouble to make things unclear, but reality is reality.

Signal has the data, but they've set up their system in a way that would require either an exploit (we've already seen examples of these) or a brute force attack to get the data requested and it's doubtful that a standard subpoena would compel them to use those methods. That said, it does leave the data vulnerable to the NSA or any other three letter agency who is willing to employ those types of methods. Signal would surely not be posting about any national security letters they were handed on their website.

Similarly anyone who can guess or brute force a four digit pin could also get the data of some users. I've posted other links with more information on all of this further down, you can check my recent comments for them, but here's this to get you started.

https://www.vice.com/en/article/pkyzek/signal-new-pin-featur...

if you're paranoid don't use a 4 digit PIN. use a passphrase. problem solved

Problem solved as long as you're threat model doesn't include three letter agencies within in the US and you don't mind that a company you're supposed to trust. and which promotes themselves to people whose freedom and or lives are on the line, isn't honest with their users about the risks of using their service.

The very first line of their privacy policy reads: "Signal is designed to never collect or store any sensitive information." which is demonstrable false. They've ignored requests to update it. (https://community.signalusers.org/t/can-signal-please-update...) I don't think you need to be "paranoid" to suspect it's probably better not to use their software when your privacy/security is critical to safety of yourself or your loved ones.

>Ever since Signal started collecting and permanently storing sensitive user data in the cloud (your name, photo, number, a list of everyone you contact using Signal.

Since when?

It was a long time ago. If you're a signal user and you're only hearing about this now, that should tell you all you need to know about how trustworthy the service is.

There were a lot of users upset about it at the time (myself included), but their protests went largely ignored. Tellingly, they've refused to update their privacy policy to reflect their new data collection practices. Personally, I take that as a huge dead canary.

https://community.signalusers.org/t/proper-secure-value-secu...

https://community.signalusers.org/t/sgx-cacheout-sgaxe-attac...

https://community.signalusers.org/t/dont-want-pin-dont-want-...

Whoa!

In Signal, Contacts’ multiple phone numbers are strictly computed each into its hashed value before only hashes of contacts being store on Signal. You can always turn that off via “Settings->Chat->Share Contact with iOS/Android” option (and it is recommended but it puts the onus of adding contacts on you, which is fine for OpSec mode). Failure to turn that off and you also get that “surprise” User just joined Signal message.

Metadata of you being stored on Signal server can be just a single user ID and heavily-ratchet encrypted before sent over network. But you would have to clear/omit your primary self contact info at OS level also.

Avatar Photo of you is problematic. Easiest not to use it in the first place. Turn off “Settings->Chat->Use System Contact Photos” option as well.

once settings are done, relevancy of PIN is reduced to (rubber-hose) OpSec and remaining forensic footprint (outside of User ID) to just within your Phone and others’ phone (and not the server, much less over network).

Turn everything off under “Settings->Privacy->Advanced” except “Circumvention” and only this one under extreme Internet duress.

What is painfully clear is while the cleartext content of your message is never stored on Signal server in any form at most states and never has your key to these content (a good thing), the association with other User ID remains forensically extractable, which is why burner phones are most helpful there there. This is where “timer” for deleting message can protect you even further (less the phone falls into the hand of an adversary within that period before timed message deletion).

If you do not mind the obtuse associativity with others, this app is excellent in keeping the actual content of your conservation off of and away from servers, network, and nation-states outside of said phones involved. Which is just fine for me and my family and close friends.

If you are striving for absolute anonymous in the area of association with others, I weakly recommended Telegram but the message is plain as day and can be read by nation-state simply because Telegram holds the encryption keys of yours.

In short, you have only one choice:

- near-absolute anonymity of message content

- near-absolute anonymity of association

It remains a hard problem.

> Contacts are strictly computed into a hashed value before only hashes of contacts being store on Signal.

Wait, are you saying only a hash is ever sent to signal's servers and stored there? How then are you able to install signal on a totally new device and have your contacts downloaded to it? You seem to think this is about contact discovery, but the data collection was about contact recovery. I've got links in other comments that describe this usage.

Data is uploaded as soon as you set a pin or opt out of setting one. If you do disable "everything" under “Settings->Privacy->Advanced” is all of the data that has been uploaded to the cloud then deleted?

By the virtue of having OS-based contact.

Which is why you disable contact.

It asked up front if you want Signal to access contact at install time.

If you say yea, then only a hashed value of each phone number found in each contact is sent. Nothing else from each and all of your contacts in your contact address book.

If you say no, then nothing of contact address book is looked at.

In a new phone, typically contact address book is empty.

If backup is restored at new phone, then it becomes important to ensure that you say no at Signal install time when prompted and asked for permission to access your contact address book.

Okay, so you're saying that if I install signal and don't give it access to my contacts (at the OS level) then when I manually add contacts in Signal itself, those never get uploaded to SVR or to storage service as anything other than a hash and those contacts can no longer be recovered in Signal using SVR?

For example see:

https://community.signalusers.org/t/faq-signal-pin-svr-kbs-s...

https://community.signalusers.org/t/what-contact-info-does-t...

I haven't seen that documented anywhere. Do you have a source?

Correction. ONLY the contacts WITHIN Signal contact address book is used.

Signal contact address book is wholly kept separate from your phone OS contact address book, even when you say yes to permission to share the OS contact address book.

If you say no to the sharing of contact, then ONLY those contacts created WITHIN Signal’s own contact address book would have each Signal contact’s phone number as numerically big-hashed (within your own phone), then only those hash value of your limited Signal contact address book would be (naturally) sent to Signal server.

This is why I said “if you don’t mind the obtuse associativity”. And that is OK for most OpSec.

What is most important here is whatever you typed, only that other contact’s phone would be able to see this, no place else. That is, until the adversary gets their hand on one of the phone before its timed message deletion period.

This is all in the source code here

https://github.com/signalapp/Signal-Android

As to the SVR and a defined PIN that activates this, this is really an “ultra-bleeding-edge super nation-state” issue. Not many can crack the SVR (outside a few professors of cybersecurity).

In the short term, preserving association seems paramount over the longer-term required to crack SVR … regularly.

I’m using PIN (and thusly SVR) because most of my contacts within Signal contact address book are named with family nicknames). So, SVR is filled with avatar, phone, last access, creation time, and its computed hash UserID values is that weak point but SVR is not that weak enough to prevent its practical usage for near-perfect message content anonymity. That’s why I ask family members not to bother with avatar and keeping real name off of OS primary user contact info.

If you are pushing the envelope of OpSec, then disabling PIN is fine too.

It doesn’t matter as long as the phone is not in the hand of adversary but steps above will make it harder, forensically.

https://blog.cryptographyengineering.com/2020/07/10/a-few-th...

If I were in Iran, disabling the pin seems like the best bet. Doing that would still cause my data to uploaded to storage service, but the only people who could access it at that point would be Signal employees or some three letter agency in the US. Same with any data you allow to be uploaded via private contact discovery.

It seems like the real problem for someone in Iran would be SVR since if you were suspected of breaking the law they could brute force your pin and get a list of your contacts then go after them. Well, I'd also consider it a problem that signal will promote itself to people whose freedom/lives are at risk without being upfront and very clear about the risks.

The very first line of their privacy policy is "Signal is designed to never collect or store any sensitive information." which is a lie, and the details surrounding this change to start collecting user sensitive data in the cloud was communicated so poorly that to this day many (most?) users are entirely unaware it's taking place, or uncertain about how it works. See for example: https://old.reddit.com/r/signal/comments/htmzrr/psa_disablin... and the OP in that thread. I can't imagine a larger red flag. That's why I suspect that signal is telling its users as loudly as they can the service is compromised. although I do wish they'd stop promoting the app to highly vulnerable people who are at real risk if their contacts are discovered.

As to “Settings->Privacy->Advanced”, the un-intuitive part is disabling everything maximizes your privacy.

And setting PIN? It’s kept within the phone’s secured memory (but NOT stored properly in the secured memory of desktops’ three main OSes).

PIN is Not easy to extract in phone OSes, digital forensically or not, except perhaps with a rubber hose.

Sure, PIN may not delayed at bad guesses. But PIN is only there to prevent casual borrower from changing Signal preference or prevent some form of evil-maid tactic.

Signal PIN is not designed nor intended to be a prevention mean during interrogation but to keep those settings in maximum privacy mode. This PIN is an excellent complement to OpSec array of protections while using Signal app.

That’s some lazy FUD. But even if that were true and the contacts weren’t encrypted and PIN entry not rate limited: What do you propose as an alternative?

It's true. I've provided some relevant links elsewhere in this discussion.

As for alternatives, I really don't know enough about the situation in Iran to say what would be safe. After they stated collecting data I personally switched to Jami for secure communications, but I'm not a whistleblower or a journalist or a freedom fighter or anything and to be honest, I haven't found anything as polished as Signal that handles both secure messaging and plain old SMS/MMS. I was a fan. It's been years and I'm still hugely disappointed.

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