Encrypting Files, Disks and Backups

Devices get lost, stolen, seized at borders and taken in raids. Encryption at rest means that whoever holds the device holds only noise, as long as it is switched off (or locked) and your passphrase is strong. It is the cheapest, highest-value security measure most people can take.

1. Encrypt the whole disk

Full-disk encryption protects a device that is off. A running, unlocked laptop has its keys in memory. Shut down (do not just sleep) before crossing a border or when a raid is plausible.

2. Use a strong passphrase

Encryption is only as strong as the passphrase. Use a long random passphrase: five to seven words chosen randomly (for example with dice and the EFF word list) are memorable and very hard to brute-force. On phones, the hardware limits guessing, but a six-digit PIN is still far weaker than a long alphanumeric passcode.

3. Encrypt individual files with age

age (https://age-encryption.org/) is a small, modern file-encryption tool with no configuration options to get wrong. It is a good replacement for most uses of PGP for files.

age-keygen -o key.txt                       # create a key pair
age -r age1yourpublickey... -o secret.tar.age secret.tar   # encrypt to a public key
age -d -i key.txt -o secret.tar secret.tar.age              # decrypt
age -p -o notes.txt.age notes.txt           # encrypt with a passphrase instead

It can also encrypt to existing SSH keys. See age: Modern File Encryption.

4. Encrypted containers and deniability

VeraCrypt (https://veracrypt.fr/) creates encrypted containers and volumes, and supports hidden volumes inside an outer volume for plausible deniability. Deniability is weaker than it sounds: a forensic examiner may find traces of the hidden volume's use elsewhere on the system, and some jurisdictions punish refusal to decrypt regardless. Know the law where you are; in some countries, refusing to provide a key is a criminal offence.

5. Encrypted backups

Backups protect you from loss; encrypted backups protect you from the backup being the weak point. A practical rule is 3-2-1: three copies, on two different kinds of media, one of them off-site.

• restic (https://restic.net/) encrypts every backup by default and works with local disks, SFTP servers and many cloud storage services.
• BorgBackup (https://www.borgbackup.org/) offers deduplicated, authenticated encryption; often paired with a remote server you control.
• Test restores regularly. A backup you have never restored is a hope, not a backup.

For a worked synchronization and recovery setup, follow Private File Sync and Backup and the Syncthing entry.

6. Passwords and second factors

• Use a password manager. KeePassXC (https://keepassxc.org/) stores an encrypted database locally that you can sync however you like; Bitwarden is an open-source hosted option that can also be self-hosted.
• Use unique passwords everywhere.
• Use hardware security keys (FIDO2/WebAuthn) or passkeys for important accounts. They resist phishing in a way that SMS and app codes do not.

7. Look ahead to quantum computers

Data encrypted today with classical public-key encryption could be decrypted later by a sufficiently large quantum computer ("harvest now, decrypt later"). Symmetric encryption such as AES-256 is not seriously threatened. For long-lived secrets encrypted to public keys, prefer tools that support post-quantum or hybrid key exchange as they become available. See Post-Quantum Cryptography.

For account authentication and spare-key planning, see Passkeys and Security Keys. Before sharing decrypted files, use Sanitizing Documents.

Sources

• age specification and reference implementation: https://age-encryption.org/v1, https://github.com/FiloSottile/age
• cryptsetup / LUKS: https://gitlab.com/cryptsetup/cryptsetup
• Apple Platform Security, FileVault: https://support.apple.com/guide/security/welcome/web
• Microsoft, BitLocker recovery overview: https://learn.microsoft.com/en-us/windows/security/operating-system-security/data-protection/bitlocker/recovery-overview
• EFF, Dice-generated passphrases and word lists: https://www.eff.org/dice
• VeraCrypt documentation, Hidden volume: https://veracrypt.fr/en/Hidden%20Volume.html
• restic documentation: https://restic.readthedocs.io/

Continue with Magic Wormhole.

Also in Privacy-Enhancing CryptographyDecentralized Storage