Comment 48 for bug 531240

I would not thing blkid (util-linux) has altered the metadata on disk.

As it got altered blkid may actually never have (occasionally) misreported anything to cause the behaviour. (The util-linux bug may not have exsted in karmic nor lucid.) I have seen blkid reporting raid correctly after installation and rebuilding the array, then things got repeatedly messed up and it reported luks (correctly as we have to assume now).

Can we be sure that blkid ever had a time when it would actually (occasionally) misreport "luks on raid" as luks in karmic?

If not this mostly puts all possibilities that can cause this to cryptsetup.

The question would then not only be whether "cryptsetup isLuks" could correctly check for luks devices to prevent any misopening. (Possibly by simply checking with blkid prior of probing the luks metadata.) But cryptsetup's initramfs scripts may itself select/detect/open a wrong device on occasions (mkinitramfs/boot).