Hi!

Cryptographic verification generally works well but there is one big
drawback: it requires correct date/time.

NTP in Qubes OS does not use any authentication by default, although it
is supported by NTP.

I conclude, that almost no one is using authenticated NTP, because there
are no instructions in a forum or blog how to enable NTP authentication
(Qubes OS specific or not). Therefore almost everyone uses standard
configuration and is at risk.

An adversary can tamper with the unauthenticated NTP replies and put the
users time several years back, especially, but not limited, if the bios
battery or hardware clock is defect.

Putting the clock several years back allows an adversary to use already
revoked, broken, expired certificates; replay old, broken, outdated,
known vulnerable updates etc.

It would be great if you could do something about it.

Cheers!
adrelanos