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Technology preview: Private contact discovery for Signal

signal.org

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Re: Technology preview: Private contact discovery for Signal

#121

Post by pokemongoaway »

mintplant wrote: post #36

In case someone from Open WhisperSystems is reading: please add stickers. Seriously, I know so many people who are on Telegram just because of its sticker system and won't consider anything without that feature. This comes up again and again in online discussions where Signal is mentioned, and it hurts to see all the care and effort the OWS team has put into providing real security rejected out of hand because of it.…

Signal needs a desktop app that doesn't suck too... Wire, WhatsApp, and Telegram all have very decent desktop apps. And WhatsApp is default end-to-end now - and I think Wire is even for groups... Had some call quality issues with Signal and started using WhatsApp again - and will test Wire for calls soon.

Re: Technology preview: Private contact discovery for Signal

#122

Post by thaumasiotes »

Animats wrote: post #120
mintplant wrote: post #41

Earlier quoted context omitted.

No, that's a different feature with the same name. That allows you to quickly layer graphics from a built-in set on top of existing photos, like in Snapchat. The "stickers" I'm referring to, in the Telegram/WeChat/LINE sense, are essentially custom emojis, or macros for sending one of a collection of reaction images as its own message. https://telegram.org/blog/stickers-revolution Various communities absolutely rely…

If you pass links to known sticker images, and the recipient has to retrieve them by means outside the Signal protocol, that reduces security. An observer can detect when a receiver fetches a sticker image, and they can tell which one. For example, noting that a message has forced the loading of collection "Gay"[1] provides much useful information to an observer. [1] http://chpic.su/en/stickers/Gayer/

So send them entirely inline. Sending a sticker is not fundamentally different from sending an image that isn't called a "sticker".

Re: Technology preview: Private contact discovery for Signal

#123

Post by pokemongoaway »

mcny wrote: post #100
orbifold wrote: post #68

Earlier quoted context omitted.

In my opinion the signal ios client is significantly less polished than the telegram client. I could convince my girlfriend to switch to telegram, after she found signal to be intolerable on her android device as well.

> In my opinion the signal ios client is significantly less polished than the telegram client. I could convince my girlfriend to switch to telegram, after she found signal to be intolerable on her android device as well. My reaction is the opposite. I love the signal iOS app because it doesn't try to do SMS. It lets you enter the code which is great if I want to use a Google Voice number instead of a carrier number (…

You think the Signal app is more polished than the Telegram app?!

Re: Technology preview: Private contact discovery for Signal

#124

Post by Animats »

thaumasiotes wrote: post #122
Animats wrote: post #120

Earlier quoted context omitted.

If you pass links to known sticker images, and the recipient has to retrieve them by means outside the Signal protocol, that reduces security. An observer can detect when a receiver fetches a sticker image, and they can tell which one. For example, noting that a message has forced the loading of collection "Gay"[1] provides much useful information to an observer. [1] http://chpic.su/en/stickers/Gayer/

So send them entirely inline. Sending a sticker is not fundamentally different from sending an image that isn't called a "sticker".

Having to send stickers every time ups the overhead. Also, if stickers are well known variable length files, it may be possible to make good guesses about which stickers are attached.

Re: Technology preview: Private contact discovery for Signal

#125

Post by fattire »

canjobear wrote: post #103

When will I be able to sign up without a phone number? The phone number requirement is ridiculous and makes true anonymity incredibly difficult.

I don't think anonymity is one of Signal's design goals-- privacy is. But fwiw there is also Wire Messenger, which looks to me to be a kind of Signal w/o the phone # requirement (you can use an email address). It claims to use the signal (axolotl double ratchet) algorithm for texts and video/audio uses webrtc https://wire.com/en/privacy/ with encryption and it's GPL'd.

Beyond that I haven't used it so can't vouch for it. Anyone else got an opinion on this Swiss app?

https://play.google.com/store/apps/details?id=com.wire

Re: Technology preview: Private contact discovery for Signal

#126

Post by rootw0rm »

davidad_ wrote: post #64
rdl wrote: post #46

This is definitely interesting (and probably the first end-user-valuable SGX-on-server application I've seen), but there are two issues IMO: 1) Intel SGX isn't really capable of resisting moderately serious physical side channel attacks by someone with physical proximity or access to the server. It's decent for low-value, or widely deployed apps where compromise of a single instance only hurts once user, but for a ce…

From what I can tell, it's worse than just Intel being a gatekeeper - every execution of "remote attestation" essentially relies upon the Intel Attestation Service to actually perform verification (or at least as the certificate authority). In a (hypothetical) world where all of Intel's security features are owned by the US intelligence community, this type of pattern seems like an awesome vector for deception ("fals…

Excellent point.

Re: Technology preview: Private contact discovery for Signal

#127

Post by [deleted] »

tptacek wrote: post #21
Confiks wrote: post #18

I don't really understand why this is an improvement on the existing architecture. In the current contact discovery implementation you need to fully trust the server, namely the open source component that is the contact discovery service. In this proposed new implementation, you still have to trust the server; you need to trust closed source processor hardware offering the Software Guard Extensions. Those extensions…

SGX attestation involves a key burned into e-fuses on processors at manufacture; the process was designed to prevent Intel from being able to derive keys used for individual enclaves. Obviously, Intel could have a malicious manufacturing process --- but then, that's the case for any piece of merchant silicon you'd use to build any computer.

[deleted]

Re: Technology preview: Private contact discovery for Signal

#128

Post by yorwba »

Animats wrote: post #124
thaumasiotes wrote: post #122

Earlier quoted context omitted.

So send them entirely inline. Sending a sticker is not fundamentally different from sending an image that isn't called a "sticker".

Having to send stickers every time ups the overhead. Also, if stickers are well known variable length files, it may be possible to make good guesses about which stickers are attached.

You could negotiate sticker sending by hash: the first message only contains the hash value, if the recipient already has that sticker stored, it can be displayed immediately. Otherwise the full data can be requested.

EDIT: That scheme can be used to probe whether or not someone already has a specific sticker stored, so it might have to be separated per-contact to avoid leakage.

Re: Technology preview: Private contact discovery for Signal

#129

Post by Spearchucker »

Started reading this article and it starts off ok and then gets all technical and I got bored.

Because, regardless of how good that solution is technically, I cannot understand what's so difficult about simply making contact discovery optional. At the user's discretion. Like you'd exchange PGP certificates.

Why, and how did user control and consent become so hard?

Re: Technology preview: Private contact discovery for Signal

#130

Post by unhammer »

fattire wrote: post #125
canjobear wrote: post #103

When will I be able to sign up without a phone number? The phone number requirement is ridiculous and makes true anonymity incredibly difficult.

I don't think anonymity is one of Signal's design goals-- privacy is. But fwiw there is also Wire Messenger, which looks to me to be a kind of Signal w/o the phone # requirement (you can use an email address). It claims to use the signal (axolotl double ratchet) algorithm for texts and video/audio uses webrtc https://wire.com/en/privacy/ with encryption and it's GPL'd. Beyond that I haven't used it so can't vouch for…

Anonymity is not the only reason for usernames though: People sometimes switch phone numbers, and some switch them more often than others (exchange/phd students going to different countries/, moving to different countries for new jobs etc).

Re: Wire, I tried it back when it had video chat (one of the few options between iPhone and Android) and Signal didn't. But I found Wire to be too unstable to be really usable. That is to say, my family members quickly got annoyed and demanded I buy an iPhone. Signal video chat solved that issue :-)

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