Any time this topic comes up, here and elsewhere, I find that most discussions revolve around different understandings and misunderstandings what people mean when they say “PGP”, and rarely lead to anything beyond that. - no this is PGP no you’re wrong that is PGP and so on and on…
(The idea of trust networks is not bad. But PGP’s implementation of them is bad.)
But PGP is useful if both sender and receiver agree to use PGP.
Anecdotally: this works until you add a third person who responds to the thread in plain text, with everything threaded beneath. Or when you do that by accident.
Applied cryptographers will tell you to use Signal or any other E2EE chat.
I think SGX is a red herring in this context. You can find it risky or not, but it's (1) not material to Signal's E2EE property, and (2) materially better than email, which sends all contact metadata in plaintext, regardless of whether you try and encrypt your message bodies. Bringing it up in this context seems like a category error.
Elaborate
There isn't one cryptosystem that does all these things. For messaging you want a carefully-defined notion of forward secrecy and post-compromise recovery, along with a careful decision about repudiation/non-repudation (1990s cryptography doctrine would suggest you just always want nonrepudiabilty, which turns out to be disastrous for privacy). For backup, you want deduplication and content addressing. For packages, you want transparency logs. You almost never want long-lived keys, but you often want identify binding.
PGP solves basically none of these problems, and offers instead a 1998 API (I'm not kidding, I thought about what year to pin it at) to basic cryptography primitives.
https://www.latacora.com/blog/2019/07/16/the-pgp-problem
Recommendations: https://soatok.blog/2024/11/15/what-to-use-instead-of-pgp/
We don't need to keep elaborating or re-litigating the same discussion. The PGP idea of "one tool to rule them all" is a terrible cryptography design, and the world is better off the sooner we stop trying to make it work.
* https://articles.59.ca/doku.php?id=pgpfan:tpp
By what I saw, there wasn't really anything anyone would care about in https://gpg.fail/ . The GnuPG problem actually declined to respond to some of them.
I'm still glad that it existed as its mere existence seems to have pushed things in the right direction as far as protecting everyone's ability to use encryption if they chose. It just never became the panacea it was envisioned to be.
Dunno that things have gotten much better over the years. End to end encryption is still fairly unusable to most. I think that rather than spending so much time on the cryptography we should instead work on a E2EE usability standard. Having everyone doing their own thing with respect to usability is not working out.
It was pretty awkward to later emerge as the PGP expert at work. I was at that time a bit shy about explaining how I got so comfortable with it.
Otherwise, anyone who is using it at all will get court ordered and then, with our current system, you just lose.
Tor solves this by making traffic entirely homogenous such that any "it could be anyone" and by making nodes extraordinarily easy to host (such that any nerd can just leave one running 24/7). Even so there are way too few nodes.
But PGP-over-email is way too metadata leaky, and if you're doing anything that actually has a threat model, you need PGP-over-email to be itself common.
Thus, participants are pooled under 1 time constrained key exchange, participants sections origins are signed/time-stamped, and the ciphertext expires on a schedule.
Why? so at some future time side-channel key exfiltration can't be used to data mine the entire history of past tapped conversations/ciphertext. Even if a private signing key is stolen, it is difficult to rebuild the lost ephemeral key session.
Have a nice day. =3