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Signal PINs

signal.org

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Re: Signal PINs

#111

Post by JoshTriplett »

kijiki wrote: post #105
JoshTriplett wrote: post #99

Earlier quoted context omitted.

I'm familiar with Signal's usage of enclaves. The case I'm wondering about is what happens if someone seized (or surreptitiously accessed) Signal's servers, ran the unmodified enclaves, but fed in different PIN requests to those enclaves in a brute-forcing attempt. What prevents that?

The enclaves will flush the data (much like the hardware you mention in your first post) after some number of wrong PIN guesses. To do this securely made the whole thing quite difficult, because it means we can never persist anything outside the enclave, or an attacker could unpersist into 1000 unmodified enclaves (who would never know about each other) and get 1000*N guesses.

That was precisely the kind of architecture I was hoping to see documented, yes. So you're locking data not just to the code running in the enclave but to the specific hardware the enclave runs on, and further doing something to prevent replay? And at the same time, providing resilience against hardware failure of the machine any given enclave runs on, and providing persistence?

Re: Signal PINs

#112

Post by moxie »

ludocode wrote: post #15

I'm extremely disappointed about how this Signal PIN rollout has been handled. Signal refused to let me view my received messages until I created a PIN. I filed a bug report about it [1]. I don't know if I was just caught in an A/B test or what because it hasn't happened to all of my Signal-using friends but it happened to me. I don't understand why it isn't just optional. They claim they want to protect my Signal da…

Right now if you re-install Signal on your device, you lose all your messages. That's already a very bad user experience, but imagine how much worse it would be if you lost your entire address book in that moment as well.

Right now that's not a problem because your social graph is in the address book on your phone, and isn't managed by Signal. This is one of the primary reasons that Signal uses phone numbers for addressing: it leverages an existing user-owned and user-managed social graph. However, what we've repeatedly heard from users is that they don't want addressing to be based exclusively on phone numbers for a variety of reasons.

If we're not using that social graph, then where does the Signal-specific social graph live? For every other app in the world, the answer is that it lives in a server-side plaintext database. Snapchat, WhatsApp, Telegram, Matrix, Wire, FB Messenger, Skype, etc etc... they're all just storing your entire social graph in a plaintext database (along with a bunch of other stuff, like your groups, profiles, etc).

Given the way that technology has developed (devices are fundamentally designed for a world of clients and servers), it's probably not possible for us to build something that makes no use of servers. Instead, we've focused on building something that doesn't store or transmit any sever-side plaintext.

For instance, when you set your Signal profile name and avatar, that lives "in the cloud" so that other Signal users can retrieve and display it. But it's encrypted (https://signal.org/blog/signal-profiles-beta/), so only your contacts can see it (not us).

With Signal Private Groups (https://signal.org/blog/signal-private-group-system/), again we have to store data "in the cloud," so that there's a canonical data source for group management, but again all of the contents are encrypted so that only group members can see it (not us).

In this case, we're using Secure Value Recovery to ensure that a future addressing scheme that's not based on phone numbers is available across app reinstalls, phone switches, phone loss, etc. We could have just done what every other consumer messaging app in the world has done (store it in plaintext on the server), but we built this instead. It is the most user-friendly option that we could conceive of while still being privacy preserving, and took a lot of engineering work.

We're going to keep looking at all the feedback we've gotten, though, to try to make it the best experience we can.

Re: Signal PINs

#113

Post by moxie »

sliken wrote: post #109
dfabulich wrote: post #93

Earlier quoted context omitted.

Read the blog post, friend! They're for restoring your data to a new device.

Still stupid, shouldn't they ask if I want that functionality? Not like it's going to be hard to brute force a user's PIN. They should explain what the pins is BEFORE they ask. What it looks like is you are going to be locked out of signal if you make a mistake. Not like the average signal user is watching the whisper systems blog.

> Still stupid, shouldn't they ask if I want that functionality?

It's kind of a difficult thing to ask. "Do you want this app to work like every other app in the world in the ways you've come to expect?" If people were to simply reinstall Signal and find that all of their contacts were gone, all of their groups were gone, all of their block lists were gone, etc... they'd almost certainly be surprised. It's not a behavior anyone expects.

Every other consumer messaging app in the world solves this by storing all of that information in plaintext on their servers. We're trying to do something privacy preserving instead, and have done a fair amount of engineering work to try to make it as frictionless as we possibly can.

If you have ideas for how we can achieve the same ends with less friction, we're definitely interested in the feedback.

> Not like it's going to be hard to brute force a user's PIN.

Check out this blog post for more information about the technology:

https://signal.org/blog/secure-value-recovery/

Re: Signal PINs

#114

Post by [deleted] »

ludocode wrote: post #15

I'm extremely disappointed about how this Signal PIN rollout has been handled. Signal refused to let me view my received messages until I created a PIN. I filed a bug report about it [1]. I don't know if I was just caught in an A/B test or what because it hasn't happened to all of my Signal-using friends but it happened to me. I don't understand why it isn't just optional. They claim they want to protect my Signal da…

[deleted]

Re: Signal PINs

#115

Post by mnm1 »

moxie wrote: post #112
ludocode wrote: post #15

I'm extremely disappointed about how this Signal PIN rollout has been handled. Signal refused to let me view my received messages until I created a PIN. I filed a bug report about it [1]. I don't know if I was just caught in an A/B test or what because it hasn't happened to all of my Signal-using friends but it happened to me. I don't understand why it isn't just optional. They claim they want to protect my Signal da…

Right now if you re-install Signal on your device, you lose all your messages. That's already a very bad user experience, but imagine how much worse it would be if you lost your entire address book in that moment as well. Right now that's not a problem because your social graph is in the address book on your phone, and isn't managed by Signal. This is one of the primary reasons that Signal uses phone numbers for addr…

The point is not to force this idiocy on people. Losing my messages and contacts when setting up a new device is actually a great feature. I regularly delete them and signal even has a feature to do so automatically. And forcing people to create a pin in the ui is just lousy ux. Until I read this article, I had no idea what that meant and just wanted it to go away. Now I want it to go away even more.

Edit: it's especially stupid if you can't use a pw manager with it. I haven't tried it because I don't want to set one. Once I'm forced, I'm going to ditch signal. Fuck that.

Re: Signal PINs

#116

Post by moxie »

ojizero wrote: post #63
aendruk wrote: post #2

Don't miss: > PINs will also help facilitate new features like addressing that isn’t based exclusively on phone numbers

I dunno but for example Wire does implement addressing without giving phone number optionally if you sign in with an email and a password, which makes me less convinced of the necessity of forced PINs in this style to enable such cases (which should be optional in the first place). Same thing with syncing across devices which requires you opt in to add email/password combo to enable those features.

They store your social graph in plaintext on their servers.

Re: Signal PINs

#117

Post by binarysneaker »

Ansil849 wrote: post #61

The way the Signal PIN feature implementation has been handled by the Signal team is extremely disappointing. The blog post completely fails to explain why this feature is mandatory, and why users are now locked out of being able to view their messages until they setup a PIN. The Signal app has now essentially taken all messages hostage, and users are unable to access messages until they create a PIN. I am a huge pro…

Completely agree. My wife showed me her phone the other day and asked "what's this PIN nonsense in signal", which I hadn't seen yet. The messaging, UI and overall UX missed the mark. What happened, Signal??

Re: Signal PINs

#118

Post by Multicomp »

sneak wrote: post #42
themihai wrote: post #26

Earlier quoted context omitted.

yeah, across devices not across the world. What stops your devices being synchronised over lan/wifi network?

The cryptographic problem of device authentication is the same whether across the room or the planet.

Then establish a handshake between two devices that you want to trust each other in the same way that you add syncthing devices.

If they still want to use a pen then there should be an option if it is an alphanumeric string to check a box that says this is managed by a password manager don't remind me for at least 6 months.

Re: Signal PINs

#119

Post by saurik »

ccktlmazeltov wrote: post #102
RL_Quine wrote: post #41

Earlier quoted context omitted.

SGX has simply just been shown to be incompatible with secure software and is impossible to justify. Signal can happily operate without the need for this sort of thing to begin with, but they keep insisting on weak solutions for no reason.

These weak solutions are actually enough to keep the government requests at bay, for the moment. Why go into crazy crypto theory if that's good enough right? That's what Apple and Google are doing as well.

As far as I understand, Apple is using dedicated secure enclave chips in their iCloud keychain service; the attacks against SGX are usually (admittedly, not always) side channel attacks due to being able to use the CPU for arbitrary insecure execution and then use that to extract information from the container. It is also my understanding that Apple controlled the keys for their hardware, and could watch themselves destroy the key: as far as they know, they can't access the data themselves and nor can anyone else... Intel SGX is subject to upgrade keys from Intel and their remote attestation can be forced by Intel: if a government wants the data they should bring the computer to Intel and start a similar battle to the one the FBI had with Apple on their older phones (where Apple already had a back door but didn't want to be forced to use it by signing a firmware to access the phone).

Re: Signal PINs

#120

Post by binarysneaker »

moxie wrote: post #112
ludocode wrote: post #15

I'm extremely disappointed about how this Signal PIN rollout has been handled. Signal refused to let me view my received messages until I created a PIN. I filed a bug report about it [1]. I don't know if I was just caught in an A/B test or what because it hasn't happened to all of my Signal-using friends but it happened to me. I don't understand why it isn't just optional. They claim they want to protect my Signal da…

Right now if you re-install Signal on your device, you lose all your messages. That's already a very bad user experience, but imagine how much worse it would be if you lost your entire address book in that moment as well. Right now that's not a problem because your social graph is in the address book on your phone, and isn't managed by Signal. This is one of the primary reasons that Signal uses phone numbers for addr…

Yeah, I get it. My non-technical wife, brother and friends didn't.
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