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Encryption and the Password Problem

Scope: the deal both tools make with you — real encryption, no back door, no mercy — and where to put the password so future-you can actually restore.

The deal

restic encrypts everything in the repository: file contents, file names, directory structure. Borg does the same in its encrypted modes. Someone who walks off with your backup drive gets noise. This is a genuine, major advantage over a plain rsync copy sitting in the open.

The price of no back door is no back door:

Please note that knowledge of your password is required to access
the repository. Losing your password means that your data is
irrecoverably lost.

That's restic's own init message, and it is not legal theater. There is no support ticket, no recovery key service, no "forgot password." The mathematics does not care about your circumstances.

Borg's extra moving part

Borg splits trust in two: a key (a file) and a passphrase. In repokey modes the key lives inside the repository, encrypted by the passphrase — lose the passphrase and the key is useless decoration. In keyfile modes the key lives in your home directory — reinstall your OS without exporting it first, and the repository on the surviving drive is unopenable even with the passphrase. Borg's init all but grabs you by the collar about this:

borg key export  REPOSITORY  encrypted-key-backup

Export the key. Store the export and the passphrase in different places. This is the single most-skipped step in all of Borg, and the most regretted.

Where mortals should keep the password

Ranked by "will future-you, mid-disaster, actually find it":

  1. A password manager — if you use one for everything else, the backup password belongs there too. (Your password manager's own database should be in the backup; keep its recovery story straight.)
  2. Written down, physically, somewhere sensible — a sealed envelope with your important papers. A backup password is used rarely and desperately; paper suits it better than another digital note that itself needs backing up.
  3. The password file (chmod 600) for the automated job — a working copy for the script, not the master record. See Automating it for the honest trade-off.

What doesn't work: memory ("I'll remember it" — you will not, in eighteen months, mid-crisis), and a text file inside the repository itself, which is a key taped to the safe.

Two smaller truths

  • Encryption protects the backup at rest, not in use. While restic/Borg runs, files are readable as usual; malware on the live machine can still reach the live files — and an always-mounted, always-writable backup drive. Versioned snapshots blunt this (ransomware can't rewrite history inside a restic repo it can't decrypt, and older snapshots survive), but the off-site copy from the 3-2-1 chapter is the real answer.
  • A very strong password you lose is worse than a good password you keep. A long, written-down passphrase of several words beats a short burst of symbols you trusted to memory. Length is strength; storage is survival.