Is a new encryption type used in 19.04?

[suplero]

Hi,

I have a dual boot system, with Kubuntu 16.04 on one drive and now Kubuntu 19.04 on a second drive, both with full disk encryption.

I can mount the 16.04 drive in dolphin when running 19.04, but I cannot mount the 19.04 drive when running 16.04.

I have used 18.04 on an encrypted drive and could mount both the 16.04 and 18.04 drives when running the alternate system.

This is an issue that I haven't seen before - not being able to decrypt an encrypted drive with a previous version.

Any insight as to what has changed? or what could be the problem?

I had thought I forgot the passphrase, but after rebooting into the 19.04 system using the same passphrase, it was the correct passphrase.

thanks
s