3 ms·

> The preparation process for sealed sender looks very complicated and iffy, but maybe someone has checked that the protocol is secure-- I don't see any reason

> The preparation process for sealed sender looks very complicated and iffy, but maybe someone has checked that the protocol is secure-- I don't see any reason for such a complicated procedure, and I see such complicated procedures as something which can only be intended to hide insecurity, but let's assume it is. I did, in fact, check it when writing TFA. > You still have connect to them and deliver this to the signal servers. They'll have your IP and will know approximately where you are physically. Okay, let's actually think this through. You have millions of people using Signal. When you send a message, the message is encrypted such that only the recipient can decrypt the envelope to verify if you're even permitted to send to them. The only thing the server gets is an encrypted envelope and some 96-bit random string that tells the server where to send the envelope. This 96-bit random string is derived from your profile key (which is also encrypted and, at minimum, rotates every time you block someone). Let's assume Signal's server has been maximally pwned by the NSA to slurp as much data and metadata as possible in the most malicious manner logically possible. In this thought experiment, they will now log things that the server currently does not because of a government-mandated implant. In this scenario, the NSA will learn: someone from an IP address send an encrypted envelope to an unknown recipient. Later, they will learn that another user (and their IP address) accessed the same envelope when downloading it from the Signal server. You might be sitting there, rubbing your hands, thinking, "Wow, we sure got them." Except that there are millions of Signal users, many whom share IP addresses over time, and you can't even be reliably sure if a given Delivery Token maps to a targeted recipient. Furthermore, you can't reliably distinguish between 1:1 messages and group messages, due to how groups are implemented (see: zkgroup). > There is no way to make this kind of thing secure without some kind of remailer system and without many peer-to-peer connections. When you say "make this kind of thing secure", are you talking about hiding IP addresses and phone numbers from Signal's servers? Or are you suggesting what Signal is already doing is not possible in the first place? Cryptography isn't magic. It is comprehensible to mortals.

impossiblefork 2y ago
Yes. So they know the IP of the sender, and of the receiver, and they know the time, and they can contact the ISP and ask them who had these IP addresses at the given time and thus determine with certainty who communicated with whom. We used a law in the EU requiring ISPs to keep track of this. It was determined to be illegal, so many ISPs probably don't store this information anymore, but I am sure that many do, and there can be other people-- maybe someone from another country that comes to your country gets jobs at ISPs to modify their software and make it do things he wants. I don't know about this Salt Typhoon, but as I interpret it, there was an excellent secure system, and then people built some kind of front end on top of it so they could enter their orders into it, and then somebody compromised that front end and basically started getting all the data that the government could order to be gathered. I'm thinking that's going to include who has what IP. I agree though, the complexity is maybe okay. It doesn't sound like a super terrible protocol or that involved. I suppose the description I saw of it felt more convoluted. At the same, I felt that the complexity of the presentation was hiding something, which I think might well be true-- it might even have been this simple fact that the central server still has every opportunity to determine who sends things to whom.
- some_furry 2y ago
  > they can contact the ISP and ask them who had these IP addresses at the given time and thus determine with certainty who communicated with whom. Public WiFi. > I don't know about this Salt Typhoon, but as I interpret it, there was an excellent secure system Hahahaha no. There was never an excellent secure system. Look at the past decade or so of SS7 attacks.
  - impossiblefork 2y ago
    Anyway, people can get IP addresses of phones, public Wifi still tells them where you were and it only takes on mistake of you connecting through your own phone for them to know certain. This taken together means there's no security with regard to contacts if the server or the network is compromised. There are excellent solutions to this: dummy messages and remailing. Without those no system can ensure that contact information is kept secret.

impossiblefork 2y ago

Yes. So they know the IP of the sender, and of the receiver, and they know the time, and they can contact the ISP and ask them who had these IP addresses at the given time and thus determine with certainty who communicated with whom. We used a law in the EU requiring ISPs to keep track of this. It was determined to be illegal, so many ISPs probably don't store this information anymore, but I am sure that many do, and there can be other people-- maybe someone from another country that comes to your country gets jobs at ISPs to modify their software and make it do things he wants. I don't know about this Salt Typhoon, but as I interpret it, there was an excellent secure system, and then people built some kind of front end on top of it so they could enter their orders into it, and then somebody compromised that front end and basically started getting all the data that the government could order to be gathered. I'm thinking that's going to include who has what IP. I agree though, the complexity is maybe okay. It doesn't sound like a super terrible protocol or that involved. I suppose the description I saw of it felt more convoluted. At the same, I felt that the complexity of the presentation was hiding something, which I think might well be true-- it might even have been this simple fact that the central server still has every opportunity to determine who sends things to whom.

some_furry 2y ago
> they can contact the ISP and ask them who had these IP addresses at the given time and thus determine with certainty who communicated with whom. Public WiFi. > I don't know about this Salt Typhoon, but as I interpret it, there was an excellent secure system Hahahaha no. There was never an excellent secure system. Look at the past decade or so of SS7 attacks.
- impossiblefork 2y ago
  Anyway, people can get IP addresses of phones, public Wifi still tells them where you were and it only takes on mistake of you connecting through your own phone for them to know certain. This taken together means there's no security with regard to contacts if the server or the network is compromised. There are excellent solutions to this: dummy messages and remailing. Without those no system can ensure that contact information is kept secret.