simplex-chat VS ContactDiscoveryService

For messaging I'm currently on Olvid (E2E with physical key exchange) but since it still use their servers, I'm currently testing SimpleX where I can host my own servers.

Notice how SimpleX (https://simplex.chat/) has no push notifications by default because of this issue.

I've been using SimpleX [0] with a couple of friends recently. It appears to work as advertised.

[0] https://simplex.chat

If you have a mobile phone number, the domestic intelligence agency knows exactly where you are at all times and any LEO (without a warrant) can also find you. In addition, there have been numerous CCC presentations showing how insecure the global (excluding US) and (separately) US carriers are guilty of promiscuous metadata trafficking ($$) and insecure SS7 setups. As a consequence, for low $, you can go to any one of several shady websites and find the last location of almost any phone number (person unique ID) globally. There are additional varying exploitable vulnerabilities depending on the exact combination of {handset x carrier x country} to impersonate them, tap their line, reveal their exact location, and redirect their phone number through a third-party handset or even a PBX. These are more expensive and some capabilities are forbidden for all but a few selective intelligence uses.

Session (Signal fork) doesn't use phone numbers. It's pretty well-designed overall and uses an onion routing approach. It's already a superset of Signal except it doesn't use phone numbers. https://getsession.org

Also look interesting:

* (unproven) https://www.olvid.io/technology

* (unproven) https://simplex.chat

PS: Using regular TOR on home broadband or cloud servers is relatively risky and inefficient. Sybil attacks on it are common. And to network operators and security agencies it gives an easy "flow tag" of your uplink and exit node data traffic as automatically suspicious.

Why not open up a Feature request on https://github.com/simplex-chat/simplex-chat/issues

[1] https://signal.org/blog/private-contact-discovery/

Signal uses SGX for remote attestation, which presumably lets the client verify that the code running on the server is a build of the OSS code and not a modified version. But I don't know the details or if this is reliable.

SGX and remote attestation described here:

https://signal.org/blog/private-contact-discovery/

Signal does private contact discovery and the effort they've gone to to do this is quite impressive.

TEEs have numerous privacy-enhancing applications that may benefit users. One of them is, as discussed earlier, private contact discovery; the Signal application uses a contact discovery service enhanced using Intel SGX, a TEE technology, to protect its users' privacy. A similar application of TEEs is performing malware analysis in a remote cloud service, so that the service may not identify users by the contents of their devices, such as the applications they have installed, especially important as 98.93% of users may be uniquely identified by the list of applications they have installed.

Signal (or, more accurately, one of its predecessors) used to use client-side private set intersection for contact discovery, but this scales poorly [1].

Now they use a solution based on Intel SGX and server-side trusted computing [2].

[1] https://signal.org/blog/contact-discovery/

[2] https://signal.org/blog/private-contact-discovery/