Die Mirrors bei Universitäten sind ebenso Privatveranstaltungen wie alle anderen Mirrors.
man pacman.conf schrieb When to Check
These options control if and when signature checks should take place.
Never
All signature checking is suppressed, even if signatures are present.
Optional (default)
Signatures are checked if present; absence of a signature is not an error. An invalid signature is
a fatal error, as is a signature from a key not in the keyring.
Required
Signatures are required; absence of a signature or an invalid signature is a fatal error, as is a
signature from a key not in the keyring.