Comment # 6 on bug 915849 from Bruno Friedmann

I'm surprized if don't work.
On my 13.1 (and previous version since age) I've manually added 

cr_sdb1  /dev/disk/by-id/ata-Corsair_Force_GT_114882050000098800C7-part1       
/root/cr_hdd1.key       noearly,luks,allow-discards

sda1 the first root system is always asking my passphrase for obvious reason.
but sdb is unlocked magically.

Did editing manually the crypptab adding the path to where the keyfile is and
then recreating initrd work?