Data backup is a valuable tool in safeguarding important data.  Data are generally backed-up onto removable data storage items, such as tape cartridges or optical discs, such that the backup data may be stored at a different geographical location to the primary data. 
By storing important data onto removable data storage items, security issues become a consideration.  For example, a visitor to a site might easily pocket a tape cartridge storing large amounts of commercially sensitive data. 
Many backup software packages provide the option of encrypting data prior to backup.  A drawback with this approach, however, is that the same software package must be used in order to retrieve and decrypt the backup data. 
Accordingly, backup data cannot be recovered using other legitimate systems where the backup software is not provided.  Additionally, software encryption increases the time required to backup data and consumes valuable computer resources.