Telegram could implement Forward Secrecy in their clients, but they choose not to

I was recently linked [this document](https://arxiv.org/abs/2012.03141), which contains enlightening information about Telegram's default ("cloud chat") functionality.

> Cloud-based chats do not provide forward secrecy, though: if, at any time, the authorization key of one of the clients is leaked then *all* the messages exchanged by that client can be deciphered.

Interestingly, Telegram has the ability to implement PFS in their cloud chats, but they [choose not to do so](https://web.archive.org/web/20191115095043/https://core.telegram.org/api/pfs).

> This article is about Perfect Forward Secrecy in cloud chats... …

article authorization client clients cloud cloud-based forward key leaked messages perfect pfs privacy secrecy security telegram