ContactDiscoveryService VS matrix-doc

[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/

Group voice and video calls are not E2EE, and use Jitsi, but this is expected to change with Native Group VoIP Signalling.

DMs in Matrix are always E2EE, and MSC3401: Native Group VoIP Signalling means there should be E2EE in group calls.

From my perspective, the really exciting thing about this that it works equally well in mobile web browsers as well as desktop web - clicking on a link on Mobile Safari should Do The Right Thing without having to install anything.

Moreover, because it's built on Matrix, MSC3401 (https://github.com/matrix-org/matrix-doc/blob/matthew/group-...) means that we'll finally have decentralised cascading video/voice conferences once the SFU (selective forwarding unit) component is added into the mix. So, for instance, users on the same homeserver will get their video feeds relayed locally with minimal latency... and then users on another remote homeserver will also get mixed locally with minimal latency, trunking the two together. If the link dies or one homeserver dies, the conference will keep going - i.e. precisely the same semantics as normal Matrix.

What metadata does Matrix protect? Encrypted state events still aren't a thing for example https://github.com/matrix-org/matrix-doc/pull/3414 This means that server admins know what groups a given account is a member of, private or not, and they also have a general idea of what the topic of said groups are, even if they're encrypted. This would be a problem for groups about sensitive personal medical issues, like a private HIV survivors or Alcoholics Anonymous group.

The protocol itself is flexible and can be changed through spec change proposals on their Github. They're currently working on implementing threads, and they recently implemented spaces, which functionally combine the concept of Discord servers and server folders. They can also be nested.

At the moment this only works with Jitsi. It will be implementet soon with MSC3401

Something we're trying to do about this on the Matrix side is MSC2716 (https://github.com/matrix-org/matrix-doc/blob/matthew/msc271...) - the ability to import archives of existing content into Matrix, and thus 'lock it open' and decentralise it for posterity: as long as one of the servers participating in that room stays alive (and the room is set up with infinite data retention, obviously) then the conversation will live on forever. (That MSC is also well worth a look for those interested in how Matrix works under the hood; MSC2716 was a surprisingly tricky problem to solve but it's basically finished now!).

Our first step will be to import all of Gitter's archives into Matrix - but we're then planning to add MSC2716 to all the existing Matrix bridges so that folks can use it to liberate chat history from Discord and Slack if desired, and avoid it getting paywalled/siloed/lost/held-hostage forever. We're also expecting to do USENET, mailing lists, forums, public IRC channels which have explicitly opted into logging... and generally archive as much possible in an open decentralised fashion, and ensure that gatekeepers can't lock up and blackhole info going forwards. After all, information longs to be free :)

by 'broken links' i guess you mean https://github.com/matrix-org/matrix-doc/issues/3628? it's a bug on the new spec website; we're working on it.