Trying to install some packages I get errors which prevent this.

error: v4l-utils: signature from "Andrea Scarpino (Arch Linux) <andrea@archlinux.org>" is invalid
error: ffmpeg: signature from "Ionut Biru <ibiru@archlinux.org>" is invalid
error: mpg123: signature from "Eric Belanger <eric@archlinux.org>" is invalid
error: clutter-gst: signature from "Ionut Biru <ibiru@archlinux.org>" is invalid
error: glu: signature from "Andreas Radke <andyrtr@archlinux.org>" is invalid
error: poppler: signature from "Andrea Scarpino (Arch Linux) <andrea@archlinux.org>" is invalid
error: poppler-glib: signature from "Andrea Scarpino (Arch Linux) <andrea@archlinux.org>" is invalid
error: libgsf: signature from "Ionut Biru <ibiru@archlinux.org>" is invalid
error: gmime: signature from "Ionut Biru <ibiru@archlinux.org>" is invalid
error: gtk-vnc: signature from "Ionut Biru <ibiru@archlinux.org>" is invalid
error: failed to commit transaction (invalid or corrupted package)
Errors occurred, no packages were upgraded.