Comment 10 for bug 1047384

By the way, this can be triaged by doing the following on the next boot (if you could get access, but it was just not the key you expected i.e. in my case)

cryptsetup -y luksAddKey /dev/sda[x]
sudo cryptsetup luksRemoveKey /dev/sda[x] 0

Check with:

sudo cryptsetup luksDump /dev/sda5