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Technology preview: Sealed sender for Signal

signal.org

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Re: Technology preview: Sealed sender for Signal

#61

Post by bigiain »

int_19h wrote: post #49
tptacek wrote: post #24

Earlier quoted context omitted.

This is the "Go y u no generics" of secure messaging. The answer is always the same: Phone numbers bootstrap a workable social network for ordinary users. Signal's goal is to transform all ordinary messaging into secure messaging. Not elite secure messaging. All messaging . The most popular messaging application in the world uses phone numbers for identifiers (as, obviously, does SMS). That's the goal they've set for…

Why do you think there are no "ordinary users" who don't have phone numbers, or don't have them in a manner that Signal needs? For example, it's pretty common for older people (especially in less technologically developed countries) to not have smartphones. I personally know at least one person who can't use Signal because they don't have a smartphone to install it on (but could install it on the desktop, if the desk…

As tptacek says - Signal isn't attempting to solve every problem or cover every edge case.

If you don't have a smartphone you can install apps on - perhaps the company making a smartphone app which happens to integrate with a desktop app as well) isn't for you. Same for "tablet users".

FWIW, you don't need to do _too_ much hoop jumping to get a non-phone device running Signal - I mainly use it on a dedicated iPod Touch, and I've got the iPhone app running on an iPad as well - in old-school 2x ugly-mode, but it works. (You do need to be aware of the risks around whatever phone number you use to bootstrap your way in possibly being reallocated. You might not want to use a 30 day burner SIM or a temporary Twilio number if you might have a targeted enough attack to impersonate you by hoovering up temporary mobile numbers...)

Re: Technology preview: Sealed sender for Signal

#62

Post by haffenloher »

bigiain wrote: post #61
int_19h wrote: post #49

Earlier quoted context omitted.

Why do you think there are no "ordinary users" who don't have phone numbers, or don't have them in a manner that Signal needs? For example, it's pretty common for older people (especially in less technologically developed countries) to not have smartphones. I personally know at least one person who can't use Signal because they don't have a smartphone to install it on (but could install it on the desktop, if the desk…

As tptacek says - Signal isn't attempting to solve every problem or cover every edge case. If you don't have a smartphone you can install apps on - perhaps the company making a smartphone app which happens to integrate with a desktop app as well) isn't for you. Same for "tablet users". FWIW, you don't need to do _too_ much hoop jumping to get a non-phone device running Signal - I mainly use it on a dedicated iPod Tou…

> You do need to be aware of the risks around whatever phone number you use to bootstrap your way in possibly being reallocated.

They recently added an optional "Registration Lock" feature to address this: https://support.signal.org/hc/en-us/articles/360007059792-Re...

Re: Technology preview: Sealed sender for Signal

#63

Post by bigiain »

Paul-ish wrote: post #34

Without cover traffic, its not clear to me that this would prevent a correlation attack from an adversary with resources.

If my IP address is my current VPN endpoint - I'm only worried about "the global passive observer" - and if I've got them curious about me there's no sensible technical measure I can take to prevent losing out to them.

As James Mickens teaches us: "YOU"RE STILL GONNA GET MOSSAD'ED UPON"

Re: Technology preview: Sealed sender for Signal

#64

Post by upofadown »

tptacek wrote: post #23

Two observations: 1. You should look into what other messengers do with sender/receiver pairs information. One very popular competing messenger logs pairs permanently, serverside, in order to make UI features work. 2. One of the least popular attributes of Signal (on Hacker News, at least) is its lack of federation and ability to interoperate with third-party clients. This feature is a pretty crystalline example of t…

Yes you can do stuff more easily if you control all parts of the network. That doesn't mean we have to give up on standards based messaging just because it is harder. In the long run silo based systems are more work because you have to reinvent everything every time you create the next entirely incompatible system. If that system doesn't catch on then you have to reinvent everything again and again until you get lucky.

This feature is an example of what happens when you don't solve the meta data properly in the first place. It doesn't really work that well but unless Signal starts routing through something like Tor (a system they don't and can't control) they are stuck with half measures.

Re: Technology preview: Sealed sender for Signal

#65

Post by eadmund »

tptacek wrote: post #29
Sir_Cmpwn wrote: post #27

Earlier quoted context omitted.

No, it's not. By requiring a phone number, Signal does not defend privacy. This is a binary question, there's not a grey area here. It doesn't matter that they're building a social network, or anything else. What matters is that it's not private so long as they require a phone number.

I'm not sure what was unclear about my summary of what Signal is doing. Here, let me put it differently for you: Signal's goal is to make all the messaging in the world that currently uses phone numbers as identifiers --- which, by a long ways, is most messaging in the world --- cryptographically secure. Hope that helps. You are welcome to have and to advocate for different goals. Please don't pretend your goals are…

> Signal's goal is to make all the messaging in the world that currently uses phone numbers as identifiers --- which, by a long ways, is most messaging in the world --- cryptographically secure.

That goal is fundamentally broken, though, because phone numbers aren’t cryptographically secure. One can use any exploit which allows one to take over a phone number to take over someone’s Signal identity. Yes, all of the target's Signal contacts will receive a message stating they his keys have changed — but they are used to that.

Signal's got some awesome crypto, but it also has some intriguing holes.

Re: Technology preview: Sealed sender for Signal

#67

Post by tptacek »

upofadown wrote: post #64
tptacek wrote: post #23

Two observations: 1. You should look into what other messengers do with sender/receiver pairs information. One very popular competing messenger logs pairs permanently, serverside, in order to make UI features work. 2. One of the least popular attributes of Signal (on Hacker News, at least) is its lack of federation and ability to interoperate with third-party clients. This feature is a pretty crystalline example of t…

Yes you can do stuff more easily if you control all parts of the network. That doesn't mean we have to give up on standards based messaging just because it is harder. In the long run silo based systems are more work because you have to reinvent everything every time you create the next entirely incompatible system. If that system doesn't catch on then you have to reinvent everything again and again until you get luck…

The Signal team essentially invented the cryptographic constructions the current wave of (good) secure messengers are based on, work for which they were awarded the Levchin Prize at RWC (for perspective, this year's winner was Hugo Krawczyk). They did the work, then published it, for the other messaging systems to adopt --- which is why you can easily get a comparable, though inferior, version of Signal's cryptography in a messenger that doesn't require phone numbers.

At some point in the future maybe the roles will reverse there, and interoperability will be a bigger issue. For now, I think Signal's userbase is benefiting from the decision. If it became necessary, presumably they can alter their stance in the future.

Re: Technology preview: Sealed sender for Signal

#68

Post by joecool1029 »

tptacek wrote: post #67
upofadown wrote: post #64

Earlier quoted context omitted.

Yes you can do stuff more easily if you control all parts of the network. That doesn't mean we have to give up on standards based messaging just because it is harder. In the long run silo based systems are more work because you have to reinvent everything every time you create the next entirely incompatible system. If that system doesn't catch on then you have to reinvent everything again and again until you get luck…

The Signal team essentially invented the cryptographic constructions the current wave of (good) secure messengers are based on, work for which they were awarded the Levchin Prize at RWC (for perspective, this year's winner was Hugo Krawczyk). They did the work, then published it, for the other messaging systems to adopt --- which is why you can easily get a comparable, though inferior, version of Signal's cryptograph…

> which is why you can easily get a comparable, though inferior, version of Signal's cryptography in a messenger that doesn't require phone numbers.

How so? Are things like OMEMO different cryptographically from Signal protocol?

Re: Technology preview: Sealed sender for Signal

#69

Post by ardy42 »

Sir_Cmpwn wrote: post #27
tptacek wrote: post #24

Earlier quoted context omitted.

This is the "Go y u no generics" of secure messaging. The answer is always the same: Phone numbers bootstrap a workable social network for ordinary users. Signal's goal is to transform all ordinary messaging into secure messaging. Not elite secure messaging. All messaging . The most popular messaging application in the world uses phone numbers for identifiers (as, obviously, does SMS). That's the goal they've set for…

No, it's not. By requiring a phone number, Signal does not defend privacy. This is a binary question, there's not a grey area here. It doesn't matter that they're building a social network, or anything else. What matters is that it's not private so long as they require a phone number.

> No, it's not. By requiring a phone number, Signal does not defend privacy. This is a binary question, there's not a grey area here. It doesn't matter that they're building a social network, or anything else. What matters is that it's not private so long as they require a phone number.

I'm not so sure. A lot of the objections to Signal using phone numbers seem similar to objecting to SSL/TLS because it's not Tor.

Re: Technology preview: Sealed sender for Signal

#70

Post by int_19h »

bigiain wrote: post #61
int_19h wrote: post #49

Earlier quoted context omitted.

Why do you think there are no "ordinary users" who don't have phone numbers, or don't have them in a manner that Signal needs? For example, it's pretty common for older people (especially in less technologically developed countries) to not have smartphones. I personally know at least one person who can't use Signal because they don't have a smartphone to install it on (but could install it on the desktop, if the desk…

As tptacek says - Signal isn't attempting to solve every problem or cover every edge case. If you don't have a smartphone you can install apps on - perhaps the company making a smartphone app which happens to integrate with a desktop app as well) isn't for you. Same for "tablet users". FWIW, you don't need to do _too_ much hoop jumping to get a non-phone device running Signal - I mainly use it on a dedicated iPod Tou…

This all has network effects. I have a smartphone, and I run Signal. But I run it much less, precisely because several people whom I want to interact with regularly are unable to, due to its limitation. This also means that I'm less likely to recommend it to others.

And I don't think that tablets are an "edge case". I mean, seriously? We're talking about millions of devices on the market. They may not be as popular as phones, but they are popular, and people use them. So when a guy uses, say, iMessage today, because it works across his iPhone and his iPad, I can't really pitch Signal to him. And that, again, has network effects.

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