## About Key Hierarchy

SME includes a comprehensive and secure system for protecting encrypted data using a hierarchy of security keys. The highest level key is the master key, which is generated when a cluster is created. Every cluster has a unique master key. In SME tape, the master key encrypts the tape volume group keys which in turn encrypts the tape volume keys using key wrapping. In SME disk, the master key encrypts the disk keys using key wrapping.

For recovery purposes, the master key can be stored in a password-protected file, or in one or more smart cards. When a cluster state is Archived (the key database has been archived) and you want to recover the keys, you will need the master key file or the smart cards. The master key cannot be improperly extracted by either tampering with the MSM-18/4 module or by tampering with a smart card.

Keys are essential to safeguarding your encrypted data and should not be compromised. Keys should be stored in the Cisco Key Management Center. In addition, unique tape keys can be stored directly on the tape cartridge. The keys are identified across the system by a globally unique identifier (GUID).

The SME key management system includes the following types of keys for SME tape:

• Master key

• Tape volume group keys

• Tape volume keys

Every backup tape has an associated tape volume key, tape volume group key, and a master key.

The SME key management system includes the following types of keys for SME disk:

• Master key

• Disk keys