@kravietz
> group chats can’t be end-to-end encrypted (E2EE), so their contents are readable to at least Telegram operators
Only today this came to me: little is known about it in the rest of the world, but due to sanctions, Russian enterprises and government organizations can't acquire proper security certificates recognised by most widely used browsers.
@kravietz
To avoid the suspiciously looking warnings they have made their own certification authority and are actively encouraging users to install this CA certificate to their systems. With this cert in the system, MITMing anything gets relatively easy.
@kravietz
Thus communication of Russians, most of which have to have this cert installed (they still have to use banks and government-provided services) over non-E2E-encrypted messengers such as Telegram are in theory "transparent" to Russian "law enforcement". I don't know though, if Telegram apps perform any checks and give you any warning if the non-expired certificate gets replaced all of a sudden.
@m0xee
Normally this would be done by the clients using HTTP Public Key Pinning (now obsolete), DANE and CAA, all of which essentially allow checking that the end user certificate has been signed by a specific CA and thus it was not “reissued” by a local security agency. But this of course depends on the client actually doing this check :)