The answer key was never on a disk

Exam morning. Forty fresh clones for the students, one grading container for the proctor. At 9:00 the key decrypts straight into the grader's /ramdisk/secrets: private, mode 0700, RAM only. Ramdisk contents never touch a disk, never appear in a snapshot, never land in a backup.

Students snapshot, break things, restore, submit. The grading script reads the key from RAM and scores each clone.

Afterward, the grading container is snapshotted and archived like everything else: and the archive holds the harness, the rubric, the submissions, and no key. A leaked archive is homework, not an answer sheet. When the host reboots, the plaintext stops existing by physics.

The answer key was never on a disk.