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Comment by 2rsf | Hacker News Reader

That is a somewhat misleading statement, you may know what's on your device but you don't know what is happening on the servers

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Its end to end encrypted chat. They could store the encrypted messages sure. I think the biggest fear people should have with signal is the client side encryption.

Right! the keyword here is "Reproducible Builds". Basically once there is documentation about how to produce the release build, you can do it yourself and compare the resulting hash with the build distributed in the Store. Generally speaking it does no come for free, but once you find a way (e.g. for iOS compiling with a specific Xcode version in a specific OS with some adjusted config) is kind of doable (except that Apple encrypts your build server side for DRM purposes, so you'll need a jailbroken phone to do something about it)

For Signal there is an open issue here for iOS [1] and some documentation for Android [2]

Some nice work about it has already be done by telegram https://core.telegram.org/reproducible-builds

[1] https://github.com/signalapp/Signal-iOS/issues/641

[2] https://github.com/signalapp/Signal-Android/blob/fab24bcd1e5...

This has nothing to do with the comment you replied to, as you have no idea what software is running on their server, so what would it even mean to reproduce it in the first place? The correct answer is merely "the server never received much in the first place so it doesn't matter as much if they stored all of it".

right, I think I messed up with the reply while I was reading other comments.

Because of public-key crypto, it doesn't matter if the servers are malicious.

not true with respect to meta data

which I don't think is as concerning, but is there a particular piece of metadata that concerns you?

I do think it is a valid concern. Over the years, various sources reported that intelligence agencies mostly use metadata (who's talking to whom, i.e. the social network) in their analysis because message content is harder to parse and understand (and, outside of email traffic, harder to obtain in the first place).

https://www.sciencemag.org/news/2016/05/your-call-and-text-r...

Metadata can be as damning as the actual message data, and in a lot of places you don't want the authorities to know that you are even communicating at all.

Certain parts of the world, people get bombed on metadata alone.

Assuming you have:

- read the source code and are satisfied that it's secure

- compiled that version of the code

- installed it on your mobile or desktop

You're still only as secure as the client on the other side of the conversation.

If that one is compromised (has not gone throught the steps above) it could very well be sending all messages in clear text to a malicious party.

Edit: formatting

Ok, sure. But what do you propose? It's still a much better situation than what we have with Whatsapp. Is there something that the Signal Foundation could do to alleviate that concern you have? There's no technical solution in any technology for preventing the other side being compromised, as far as I can see.

At present I'm choosing to trust Signal.

That doesn't mean I blindly trust them, only that despite seeing potential for abuse I judge that they have more incentive to be telling the truth than not.

Also check the comment by user faitswulff where they mention how they have been subpoenaed "and could only supply account creation time and last connection time".

Matrix since you can self-host and have control while still being able to communicate to other people on it through federation

>>> You're still only as secure as the client on the other side of the conversation. If that one is compromised ... it could very well be sending all messages in clear text to a malicious party.

>> There's no technical solution in any technology for preventing the other side being compromised, as far as I can see.

I don't know Matrix, but I can guarantee that it doesn't solve the problem of a compromised client obtaining the messages willingly sent to it.

Yeah and since you have the possibility of dealing with state actors with deep pockets, you have to wonder if Android or iOS doesn't have the ability to copy your private keys and send those off somewhere for storage. Because of signal's popularity, it feels pretty possible to me.

If the NSA did have it backdoored somehow through the OS, it's a good bet they'd force LE agencies to use parallel construction to keep that information top secret.

That is why we really need open source hardware and OS's. A good (or even functional) open linux phone can't come fast enough.

If your adversary is state actors with deep pockets or the NSA, you've lost already. No amount of opsec cosplay is going to save you.

Your solution?

* Magical amulets?

* Fake your own death, move into a submarine?

* YOU’RE STILL GONNA BE MOSSAD’ED UPON

https://www.usenix.org/system/files/1401_08-12_mickens.pdf

AOSP (Vanilla, GrapheneOS, CalyxOS) doesn't have this capability.

The Google Play Services app/package? Heh...

The server can MITM the public keys, providing you with a key from the server instead of the key from your conversation partner.

It very much does matter if the server is malicious.

Not if the keys are generated by the client.

Signal also offers to label contacts for which you could verify the authenticity by another way.

Doing a video call with the contact can be a simple way to clear doubts, even if it is not a proper different channel.

This is false. A video call will not prevent or detect MITM. You may be suggesting that a video call is used to authenticate the key, which is certainly a step in the right direction, but I don't think Signal supports this.

It will, because it will prove (or give you a lot of confidence) that the agent who sent you their public key is your legit correspondent.

This uses the fact that the client on each side is open source and inspectable, so that each side knows that they sent only the public key that they generated on their own device.

PS: to answer your last sentence, Signal allows you to flag specifically contacts that you managed to verify. Which is technically equivalent to say that you verified that the public key is theirs.

Yes, but it doesn't support doing that whilst in a video call with them.

[edited]

Indeed it is far from straightforward that merely doing a video call suffices to check the keys.

Signal is famously using a special protocol for secure key sharing through the server, which I have not studied.

But as said by another comment, there is no way around verifying explicitly the public key using an independent channel.

Video calls alone won't stop a MITM attack. They would just send both video streams along, and record both sides.

Signal does have the capability to have a verification phrase displayed, which is generated from the session key. Reading that off can make the video more difficult to MITM, because then they'd have to morph the audio to match the phrase, and if it's done after the video is setup, morph the video as well. Not impossible, but difficult.

If you are paranoid, you can do public key verification through another channel. People with high risk profiles should do this.

Key authentication is not for the "paranoid" or simply those with "high risk profiles", otherwise every web browser in the universe wouldn't do it by default on every single connection to every single website. It is a normal, routine thing that is expected in all modern secure communications systems.

Please don't spread this harmful meme.

We've got certificate authorities to centralize trust for server public keys. And those require trusting organizations that lots of people don't want to trust. We don't have an equivalent system for individuals. There is no trivial push-button key verification process for peer-to-peer communications. Key signing parties suck and never worked. Key validation for things like Signal is nicely automated if you are physically near the other person. But beyond that it is tricky.

It is hard enough to get my parents to use a secure messenger. If I told them they needed to do a key verification process for every person they ever communicate with... they'd just go back to facebook messenger or sms.

I think it is completely reasonable for somebody to say "I don't care enough to worry about validating public keys" while also educating people like journalists about how to do that correctly.

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