Update only archlinux-keyring and try again.
# pacman -S archlinux-keyring
# pacman -Syu
In some cases you may need to re-populate the keyring.
# pacman-key --init
# pacman-key --populate
The beloved lightweight distro
Update only archlinux-keyring and try again.
# pacman -S archlinux-keyring
# pacman -Syu
In some cases you may need to re-populate the keyring.
# pacman-key --init
# pacman-key --populate