cant upgrade any help

Total Download Size:      0.19 MiB
Total Installed Size:  3180.91 MiB
Net Upgrade Size:       187.10 MiB

:: Proceed with installation? [Y/n]
:: Retrieving packages ...
 light-locker-1.6.0-1.1-i686         66.2 KiB   331K/s 00:00 [################################] 100%
 lightdm-gtk-greeter-settings-...   123.6 KiB   353K/s 00:00 [################################] 100%
(520/520) checking keys in keyring                           [################################] 100%
(520/520) checking package integrity                         [################################] 100%
error: light-locker: signature from "Rob McCathie <korrode@gmail.com>" is unknown trust
:: File /var/cache/pacman/pkg/light-locker-1.6.0-1.1-i686.pkg.tar.xz is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: lightdm-gtk-greeter-settings: signature from "Rob McCathie <korrode@gmail.com>" is unknown trust
:: File /var/cache/pacman/pkg/lightdm-gtk-greeter-settings-1.2.0-1-any.pkg.tar.xz is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n]
error: failed to commit transaction (invalid or corrupted package)
Errors occurred, no packages were upgraded.