Encryption and Cybersecurity
Scope
This domain tests drive-based encryption, the key hierarchy, key-manager dependency, and the security properties of offline media.
Core rules
- LTO-4 and later drives encrypt with AES-256-GCM in the drive, below the application. The host or library instructs the drive to encrypt; the backup stream and, in library-managed mode, the backup software are unchanged.
- Two key levels: a data encryption key (DEK) per cartridge, wrapped by a key encryption key (KEK) held by the key manager. The wrapped DEK travels with the tape; the KEK never does. KMIP is the usual protocol between library and key server.
- Lose the key and the data is gone permanently. There is no back door and no drive-side escrow. Key manager backup, escrow and a rehearsed recovery test belong in the design, not the appendix.
- Encryption policy must be explicit: which media pools, which applications, which libraries, and what happens to unencrypted legacy tapes. Mixed or inherited policies are where audits find gaps.
- Offline tape is a real air gap: no credentials, no network path, no share to attack. Combined with WORM and encryption it is the standard ransomware-recovery tier.
- TapeAlert flags and LTO-CM counters provide media and drive health signals; retain them as audit evidence of handling.
Worked example
An LTO-7 tape written encrypted in 2019 must be restored in 2025 on an LTO-9 drive. The LTO-9 drive reads LTO-7 and is encryption-capable, so media compatibility is fine. The restore still fails unless the key manager is reachable and holds the same key alias, because the drive cannot derive the KEK. Test restores with the key server in the loop, not just the drive.
Traps
- Assuming LTFS or the backup application encrypts when the drive is doing the work.
- Storing keys alongside the tapes they unlock.
- Encrypting on the host first, then wondering why the drive achieves no compression.