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Signal PINs

signal.org

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Re: Signal PINs

#121

Post by joecool1029 »

moxie wrote: post #113
sliken wrote: post #109

Earlier quoted context omitted.

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 beha…

>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.

I see a lame excuse.

Lets be real: Groups have never worked very well in Signal, so people use alternatives. It's been my experience that at some point it screws up and everyone has to delete the group and we start over again.

Contacts are stored by Apple, Google, Microsoft, and/or their work email provider for a large majority of the population. Only the minority using burners might care and they are likely already used to setting up lists every time they burn a device.

Put a checkbox in the app for: 'Store my blocklist and profile info in Apple/Google's backup system. This will share info with them'. Some users will want that, others won't. Quite a few people would like to have Signal's message backups included in an offline iOS backup, their complaints have fallen on deaf ears. Stop pontificating and give the option. It was a bigger compromise on your end creating a Signal Desktop app than it was to provide an option to include message exports in an encrypted backup.

Say what you will about Telegram, they made a much more reasonable compromise with their 'secure messaging'. This feature is not in their desktop apps as the attack surface of a desktop/laptop is too large. Secure chats instead focus on ephemerality and are torn down after completion. It's a more realistic threat model.

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

Ah yes, the complex technology that relies on the insecure broken thing from Intel: https://arstechnica.com/information-technology/2020/03/hacke...

Re: Signal PINs

#122

Post by Multicomp »

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…

I have two comments, one about the signal pin implementation as it exists now, and one possible Avenue forward to obviate the need for signal pins under certain circumstances.

for signal pins today, there should be an option to not be reminded of it because the user has a password manager. The option to not remind could be buried in the settings with a big scary warning that says if you do not get reminded again you will lose everything.

Signal pens can be bypassed entirely in the cases where users have multiple devices such as a linked phone or desktop.

One device sets a strong alphanumeric pin and sends it to the server. Users can share an ID unique to each signal installation on each of their devices. Each individual device has the ID for every other individual device. For each device that does not know the signal pin, it can request it from a device that does have the signal pin and or the device that made it. If a signal installation has the pin and gets a request for the pain from another device ID that it knows about, it provides it.

This device ID exchange behavior is used in syncthing to support e2ee peer-to-peer file sync, and could be used for syncing metadata in the situation where one device has its installation lost or reinstalled and needs to be repulled from the central servers.

An existing device(s) is told the Id of a new device and the new device is told about the existing device(s). None will communicate with the other without already having the user enter the device ID.

Once the two installations have handshaked, the existing device tells the new device what the seignal pin is and it can download it from the signal server.

For users who do not wish for cloud storage could have their device treat another device as the canonical source for the data post handshake and the data could be synced over lan or using stun/turn.

Re: Signal PINs

#123

Post by wl »

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…

> 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.

How about letting people back this up? There's no way to do this on iOS or in the desktop app. You're solving a problem of your own making with a solution your core audience of privacy conscious users does not want.

Re: Signal PINs

#124

Post by godelski »

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…

> 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.

Why not just allow users to load their data into the cloud with a pin or password? My friends that use Signal because I pressure them into it (remember, that's why a lot of people use Signal) just want a one click upload/download. Generally these are also iPhone users, which currently doesn't allow this. Why not just give a one-click option to sync into drive or iCloud? Make it optional too (for the privacy folk who are generating your userbase). Doesn't this solve the whole problem?

Re: Signal PINs

#125

Post by kijiki »

JoshTriplett wrote: post #111
kijiki wrote: post #105

Earlier quoted context omitted.

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?

Yeah, there is a 32 byte random serviceid generated inside the enclave when it starts in "new" mode, so it is locked to the serviceid, not the HW, so we can migrate off failing/failed hardware. The only way to get a non-random serviceid is to have keyspace transferred to you from an existing enclave, after mutual attestation. Clients verify the serviceid after attestation verifies the enclave.

Each partition of the keyspace lives on a 5 node cluster, running RAFT inside the enclaves to ensure the pin guess count is consistent.

If a node fails, or is failing, or we need to do maintenance, we transfer the partition from the old nodes to new ones, which transfers the serviceid as well. If you start a new enclave from scratch, it'll generate a new serviceid, and clients won't talk to it, and existing partitions will refuse to transfer to it since it already has a serviceid. In fact, it won't even be listening for incoming transfers, since it thinks it owns the entire keyspace.

We can also do a partial partition transfer that leaves the source cluster live, which we use to split up the keyspace more when we need to scale up.

There is no persistence (wouldn't be secure, attackers could do many parallel enclave resumes to get extra guesses), so the 5 nodes in the cluster live in geographically separated data centers, and we're real careful about things that could kill a node or process.

Re: Signal PINs

#126

Post by kijiki »

ccktlmazeltov wrote: post #106
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?

if it's anything like what other big players are doing: the attempts are limited and the code will destroy its knowledge of the key once you reach this limit. Looking at the code quickly I see that nothing is documented and it's not clear what code gets executed there. So good luck understanding what they're doing. But it seems to be using Raft, probably to bring several HSMs to consensus on what's the state of the n…

That isn't quite how it is implemented, there are no HSMs, we use SGX for that function instead. See my reply to Josh's follow up for details.

You need a random id not the phone number, so other users can't do guesses unless they get that random id somehow. The ID is stored on the phone, and if you lose it, when you reinstall Signal, the signal server will give it to you after SMS phone # verification.

A sim-jacker could nuke your key, but that seems like a lot of work for griefing. Signal of course, has the plaintext random id, so they could nuke your backup, but there are tons of ways Signal can DoS attack their own service. Stopping paying for the servers, for one.

Re: Signal PINs

#127

Post by balladeer »

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…

If Signal PINs came with a feature that made it possible for me to not have my identity tied to a phone number I'd have understood (and accepted?) this release and rollout better.

Re: Signal PINs

#128

Post by aoeuhtns »

Don't understand the negative comments here and on their subreddit... Secure Value Recovery and the associated PIN seems like an advance in the state of the art -- nobody else seems to do this. All users have to do is remember a few numbers.

I find it surprising that many users got so upset by the software asking them to set a password that they removed the app... seems a bit extreme. I guess if it was part of a "sign-up" flow, people would have been primed for it... But even then, it takes like just a minute to do it? /shrug

Re: Signal PINs

#130

Post by petre »

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…

One alternative is Wire. I use both.

My partner uninstalled Signal when it failed to work from within the UAE and could not contact me. If she wouldn't have done it then, she would now with this PIN nonsense. At least we can text via Wire.

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