Sierra encrypted external hard drive and Mountain Lion

[Poncho]

I right-clicked on my external hard drive which I use to clone my Mac. It encrypted fully. All OK. I am using Sierra.

I then plugged it into my laptop running Mountain Lion. Splash screen comes up asking for password. Enter password but it says the disc is unreadable and asks me to initialize it.

Go back to Mac running Sierra and all works perfectly.

According to:

http://www.techmeback.com/blog/files/encrypting_a_usb_drive_on_a_mac_made_easy_sierra.html


a disc encrypted on Sierra should be readable on any Mac going back to Lion.

Have I misunderstood this?

 

[Fishrrman]

Take the drive to Sierra.
Decrypt it.
Take it to the Mountain Lion Mac and try again.