This should be added for encryption/decryption purposes. It is pretty common functionality, if you're dealing with security-related applications or sensitive information...
There are pure Lua implementations out there, but the problem is they perform pretty slow, therefore a native (Java) function would be much more useful.
One area comes to mind, in particular I think this would also be helpful to have in rednet area, as it would provide a decent protection layer, assuming you store the keys in a safe manner.