Adding encryption to disk backup set

[cgtyoder]

Using: Retrospect 7.0.344, Update 7.0.12.105 on Windows Server 2003 SP2.

 

I know that encryption cannot actually be added to a backup set, but what is the least painful way to "add" it and still retain backup info? Create a new disk backup set, and then add members from the previous unencrypted backup set? (Is this even possible?) Thanks for the assistance.