TLDR: an e2ee channel means "everything passing over this channel is super secure and private, but it needs some keys for this to work". e2ee means something: you can not care about most issues with delivery and protection and such, but you need to care about the keys. if you don't do that, you are probably ruining the security of such e2ee channel

end-to-end-encryption solves one issue: transport over untrusted middleware, doesn't mean much by itself. it's being flung around a lot because without proper understanding sounds secure and private.

it's like saying that i ship you something valuable with a super strong and impenetrable safe. but what do i do with the key? e2ee is the safe, solves the "how can i send you something confidential when i dont trust those who deliver it", and it means much! it's a great way to do it.

but it solves one problem giving a new one: what to do with the key? this usually can be combined with other technologies, such as asymmetric encryption (e.g. RSA), which allows having keys which can be publicly shared without compromising anything. so i send you an impenetrable code-protected safe with an encrypted code attached, and only your privkey can decrypt the code since i used your pubkey!

(note: RSA is used for small data since encryption/decryption is cpu intensive. usually what happens is that you share an AES key encrypted with RSA, and the payload is encrypted using that AES key. AES is symmetric: one key encrypts and decrypts, but AES keys are small. another piece of technology attached to make this system work!)

but now comes the user-friendliness issue: very few are big enough nerds to handle their keys. hell, most folks don't even want to handle their passwords! so services like matrix offer to hold your keys on the server, encrypted with another passphrase, so that you don't need to bother doing that, just remember 2 passwords or do the emoji compare stuff. it's meh: compromising the server could allow getting your keys and kinda spoils e2ee, and once i stole you one password i can probably steal you both, but it's convenient and reasonably secure for most. you can absolutely opt out, but every time you log from a new device, you can't read anything sent before unless you export and import your keys manually.

what does whatsapp do? i don't know! but it kind of magically works. if they do e2ee, where are the keys???? how does meta handle reports if messages are e2ee???????

i'm not sure about signal but everyone praises it so i guess it's good? also it seems you can't restore messages via network, you need an export from a previous install, so it seems your keys live inside your app data, which is good and safe i guess.

also, e2ee works if you can trust the key you're sending to! as mentioned in the 'activitypub keys' section before, if you ask a middleman the key for your recipient, can you trust that's the real key? e2ee doesn't cover that, it's not in its scope

so what does e2ee mean? it means: super strong channel, ASSUMING keys are safe and trusted. e2ee as a technology doesn't solve "all privacy" or guarantee that nobody snoops in per se. it offers a super safe channel protected by keys, and lets you handle those keys how you more see fit. which meaning deciding who you trust to send, how you let others know how to encrypt for you (aka share your pubkey) and how you will keep your privkey safe.

thanks for coming to my TED talk btw