The "Change Encryption Key" function is used to generate a new AES encryption key.  This is useful for redeploying a DataLocker to a new user, for example, if a company needs to reissue a used DataLocker to a new employee, changing the encryption key will make all previously stored data unreadable.

Changing the encryption key is irreversible, and makes 100% of your data unreadable.  Please use it with caution!