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Technology Preview: Signal Private Group System

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Re: Technology Preview: Signal Private Group System

#11

Post by squarefoot »

myu701 wrote: post #5
noja wrote: post #3

Earlier quoted context omitted.

> This is either a reason you love Signal (raises hand) or can't stand Signal. Eh? Why either or? (and why are there people who can't stand it?)

I love Signal, and upsell it whenever I can. Signal has its ideosyncratic parts, some of which are being worked on, others not so much. Some of the more visible ones are IMO: Signal forces users to use phone numbers; some people don't like this because they want to use multiple ephemeral usernames so they can be 'Joe' to friends, 'kleptoclown' to their github group, 'dungeonmaster42' to their DND group, 'joesolutione…

"Signal forces users to use phone numbers"

Which is number one reason why I'm not even considering it

"some people don't like this because they want to use multiple ephemeral usernames"

That's not my reason: I don't want people I don't know to get my phone number through other people I know and trust, but are used to share everything online. Of course that would be possible without any social application as well, though using one makes it much more natural.

Then this one from their site: "Multiple mobile devices and Android tablets are not currently supported"

Triple facepalm here: this makes it even worse than Whatsapp I use (read: am forced to use) on an old tablet. Whatsapp sucks badly just at everything (didn't I write I'm forced to use it?) but at least I can read what I write.

Downvotes welcome, though advice on secure+open alternatives that don't assume I have a smartphone (I haven't one and don't plan to) would be more informative.

Re: Technology Preview: Signal Private Group System

#12

Post by 0xCMP »

SheinhardtWigCo wrote: post #9

The point of this seems to be hiding the identity of users when they fetch or modify group attributes - but why? The user’s identity is otherwise known to the server: they know that account X was accessed by IP address Y, and that IP address Y fetched metadata for group Z, therefore account X is in group Z. They can also figure out group membership by tracking clusters of messages that are sent simultaneously. What a…

They do not know that information unless they’re monitoring on-the-server in the clear. They simply know they’re talking to Signal servers. This new feature protects in the case of Information Requests because they themselves don’t know who is in what groups.

Re: Technology Preview: Signal Private Group System

#13

Post by SheinhardtWigCo »

0xCMP wrote: post #12
SheinhardtWigCo wrote: post #9

The point of this seems to be hiding the identity of users when they fetch or modify group attributes - but why? The user’s identity is otherwise known to the server: they know that account X was accessed by IP address Y, and that IP address Y fetched metadata for group Z, therefore account X is in group Z. They can also figure out group membership by tracking clusters of messages that are sent simultaneously. What a…

They do not know that information unless they’re monitoring on-the-server in the clear. They simply know they’re talking to Signal servers. This new feature protects in the case of Information Requests because they themselves don’t know who is in what groups.

You either have to trust the server operator not to keep logs, or assume they are keeping logs and _do_ know what groups you’re in. In either case, what is this fancy crypto scheme actually buying you?

Re: Technology Preview: Signal Private Group System

#14

Post by tptacek »

pepijndevos wrote: post #10

I really want Signal to succeed. Or rather, I want anything that has decent cryto and is not FAANG to succeed. The problem is not which messaging app I want to use, it's which messaging app my friends are using. That said, if I had to choose, I think Matrix has a slight edge in my books because it's a protocol rather than a silo. Even though Signal is private and open source, they are hostile towards people running t…

Matrix and Signal aren't comparable from a security perspective. Because Matrix is a protocol rather than a silo, many (most?) of its implementations don't even support E2E, and because Matrix has its roots in an ecosystem where E2E was a nonstandard add-on, Matrix will never be as safe as Wire or Signal.

Re: Technology Preview: Signal Private Group System

#15

Post by Forbo »

SheinhardtWigCo wrote: post #13
0xCMP wrote: post #12

Earlier quoted context omitted.

They do not know that information unless they’re monitoring on-the-server in the clear. They simply know they’re talking to Signal servers. This new feature protects in the case of Information Requests because they themselves don’t know who is in what groups.

You either have to trust the server operator not to keep logs, or assume they are keeping logs and _do_ know what groups you’re in. In either case, what is this fancy crypto scheme actually buying you?

> You either have to trust the server operator not to keep logs

You don't have to trust, you can verify. This has been proven in court: https://signal.org/bigbrother/eastern-virginia-grand-jury/

Re: Technology Preview: Signal Private Group System

#16

Post by tptacek »

SheinhardtWigCo wrote: post #13
0xCMP wrote: post #12

Earlier quoted context omitted.

They do not know that information unless they’re monitoring on-the-server in the clear. They simply know they’re talking to Signal servers. This new feature protects in the case of Information Requests because they themselves don’t know who is in what groups.

You either have to trust the server operator not to keep logs, or assume they are keeping logs and _do_ know what groups you’re in. In either case, what is this fancy crypto scheme actually buying you?

The fancy crypto is what allows them not to (effectively) keep those logs in the first place. If you build this feature without the fancy crypto, then even if you say you're not logging this stuff, you (effectively) are, because your system depends on durable access to that metadata in order to function. This is, for instance, the major security difference between Signal and Wire.

One strong indication you have that Signal isn't logging this stuff is that they had to wait until they were able to advance the state of the art in anonymous credentials in order to implement group access control at all.

Re: Technology Preview: Signal Private Group System

#17

Post by eipi-1 »

pepijndevos wrote: post #10

I really want Signal to succeed. Or rather, I want anything that has decent cryto and is not FAANG to succeed. The problem is not which messaging app I want to use, it's which messaging app my friends are using. That said, if I had to choose, I think Matrix has a slight edge in my books because it's a protocol rather than a silo. Even though Signal is private and open source, they are hostile towards people running t…

They provide good reasons for doing so [1]. I share your hope that "anything that has decent cryto and is not FAANG" will succeed and I would prefer it to be a federated system but I also see what moxie describes in the article. Basically federation only works on a lowest common denominator. This means progress is very slow or impossible. Comparing the current state of the Matrix ecosystem and Signal I find it a lot easier to convince friends and family to join Signal. After all, that is what makes a messenger useful.

Anyway I wish both projects the best of luck.

[1] https://signal.org/blog/the-ecosystem-is-moving/

Re: Technology Preview: Signal Private Group System

#18

Post by juped »

tptacek wrote: post #6
myu701 wrote: post #5

Earlier quoted context omitted.

I love Signal, and upsell it whenever I can. Signal has its ideosyncratic parts, some of which are being worked on, others not so much. Some of the more visible ones are IMO: Signal forces users to use phone numbers; some people don't like this because they want to use multiple ephemeral usernames so they can be 'Joe' to friends, 'kleptoclown' to their github group, 'dungeonmaster42' to their DND group, 'joesolutione…

It's really an engine for revealing people's true preferences for messaging, which, for many people, tend to be that they want all the ergonomics of Slack a lot more than they want cryptographically sound secure messaging. What's hopeful in all this is that Signal is, slowly, catching up. Slack can roll out new features just by assigning a couple developers to it, and Signal has to coordinate new cryptographic resear…

Why would Signal (a drop-in SMS replacement) be compared to Slack?

Re: Technology Preview: Signal Private Group System

#19

Post by JoshTriplett »

tptacek wrote: post #2

Again, in the theme of "features every group messaging system had already, but Signal didn't, because they hadn't figured out a way to implement it without turning Signal's central servers into a database of who's talking to who about what". Signal didn't even have user profiles until recently, for the same reason. Here, they've slightly expanded the state of the art in MAC-based anonymous credentials to accomplish t…

Honestly, the one and only feature I'm missing in Signal that would let me use it and recommend it to everyone without reservations (rather than exclusively for ephemeral-only communication) is the ability to keep identity and full message history when moving to a new device.

Today, on iOS, you can't move your Signal history to a new device, and on Android you can only do so by manually making an encrypted backup file and writing down a 30-digit passcode, completely separate from the normal Android process of moving to a new device.

People keep long histories of messages, going back a decade, containing pictures and memories that aren't stored anywhere else. Message history is valuable data.

This doesn't seem like a "new cryptographic research" problem, this seems like a "well-established crypto (encrypted files) plus integration with standard device backup/migration" problem.

I really like Signal, I think they're doing things very well, and I wish I could use it without being constantly at risk of data loss. And this doesn't seem like an uncommon request, from what I've found.

Is there something I'm missing that makes this a hard problem? Or is it just a problem that nobody has prioritized?

Re: Technology Preview: Signal Private Group System

#20

Post by tptacek »

juped wrote: post #18
tptacek wrote: post #6

Earlier quoted context omitted.

It's really an engine for revealing people's true preferences for messaging, which, for many people, tend to be that they want all the ergonomics of Slack a lot more than they want cryptographically sound secure messaging. What's hopeful in all this is that Signal is, slowly, catching up. Slack can roll out new features just by assigning a couple developers to it, and Signal has to coordinate new cryptographic resear…

Why would Signal (a drop-in SMS replacement) be compared to Slack?

Because we're talking about group messaging here.
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