Right now I believe that tor v3 onion services are the closest we have to practical approaches to minimize metadata (far from perfect, and the price point for defeating it gets lower)
There has also been a lot of really cool research in the last few years specifically on new cryptographic protocols in aid of solving this problem in a way that is different from the "we need a verifiable mixnet / PIR" approach see keywords: fuzzy message detection / oblivious message detection / OMR
@sarahjamielewis delta chat really does have a history of completely misapplying technical or academic terms and then using their wrong definitions to claim security properties they fundamentally do not offer. It's rather baffling and quite disappointing. 
@sarahjamielewis indeed, resistance against traffic correlation is a big challenge. Usually, for instant messaging Signal is used as a comparison basis. Its amazon/cloudflare/microsoft hosted servers, like chatmail relays and their hosters, can do adverserial traffic analysis, irrespective of how much metadata travels in the messages. The question maybe is if there is anything inherently not doable with the email system and in particular chatmail clients that can be done with Signal clients.
@delta @sarahjamielewis
running a chatmail relay inside DeltaChat and P2P communication might be difficult with the default email protocol
Resisting such correlative models is very much still an active research that spans anonymous communication networks / mixnets / application security and many other subfields.
It's something I've been working on for over a decade, and while I am very proud of the work we've done on @cwtch there is still a long way to go (if you want to dig into what we consider the security model here you can check out our security handbook https://docs.cwtch.im/security/risk)
Right now I believe that tor v3 onion services are the closest we have to practical approaches to minimize metadata (far from perfect, and the price point for defeating it gets lower)
There has also been a lot of really cool research in the last few years specifically on new cryptographic protocols in aid of solving this problem in a way that is different from the "we need a verifiable mixnet / PIR" approach see keywords: fuzzy message detection / oblivious message detection / OMR
@sarahjamielewis sadly while on paper Tor is nice, on practice on the field it just gets blocked, for example during protests in Cuba some years ago Tor and hence apps like Briar simply stopped working completely, I think the same is happening in iran right now, so at that point the metadata protection it gives is useless, hope there is some other solution, but if your app only works over tor it is almost useless I am afraid
@sarahjamielewis
>Right now I believe that tor v3 onion services are the closest we have to practical approaches to minimize metadata
What about #I2P destinations?
Since the Tor project is located in the USA and is partially centralised.
There was a project that did that but it hasn't been updated for years: https://vituperative.github.io/i2pchat/
@sarahjamielewis We are somewhat interested in running chatmail relays as .onion services: https://github.com/chatmail/relay/issues/487
There is also an experimental yggmail backend, anyone can build a local IMAP+SMTP server for any store-and-forward network and use Delta Chat as an UI: https://support.delta.chat/t/bluetooth-and-or-wi-fi-direct/3164/5
Not having a good UI is a large problem for research projects, last time I tried katzenpost it did not work and now the UI is even archived: https://github.com/katzenpost/katzen/issues/48
My personal long term take here is that a good solution for this problem might look something Niwl ( https://git.openprivacy.ca/openprivacy/niwl ) which is a prototype I built some years ago based on playing with FMD/FuzzyTags
i.e. how can we approximate a mixnet/PIR system with untrusted actors in a way that minimizes communication bandwidth?
As that work says, and what I am slowly convincing myself should be emblazoned across every project that even remotely attempts to make progress on communications privacy: hic sunt dracones
(But that isn't good marketing, so...)
And since it's come up:
If you are willing to trust a routing intermediary (and anyone who may force that intermediary to act e.g. a government) - then you don't have to worry about such attacks.
But in that case, just use Signal - it has a lot of other nice cryptographic properties that apply in that model.
(Signal also make various claims about metadata, I disagree with many of those claims, some I find outright ethically dubious as a privacy researcher - but you should just use Signal)
@sarahjamielewis do you detail your full stance toward Signal as an expert in an article somewhere?
Do you have a writeup of sorts to what you think is wrong?
There's a lot out there that explain how signal works and then how that increases privacy, but i have not encountered much *credible* critical texts, and i don't know where you might have written about that.
(For those who care: Signal used to place a heavier emphasis on trusted execution environments as a mechanism for protecting metadata, despite TEE's having been incredibly broken in most realistic threat setups forever, in recent years Signal switched to a "we don't collect anything" messaging which is fine for what Signal is, but I do wish they would be more honest about what they *could* be compelled to collect in theory. (which in reality is: a lot of metadata))
@sarahjamielewis @cwtch Slightly offtopic I’m reminded of this little gem https://kieranhealy.org/blog/archives/2013/06/09/using-metadata-to-find-paul-revere/
