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amcrypt — reference crypt program for Amanda symmetric data encryption




amcrypt requires aespipe and gpg to work. Aespipe is available from http://loop-aes.sourceforge.net

amcrypt will search for the aespipe program in the following directories: /usr/bin:/usr/local/bin:/sbin:/usr/sbin.

amcrypt calls amaespipe and pass the passphrase through file descriptor 3. The passphrase should be stored in ~amanda/.am_passphrase.

How to create encryption keys for amcrypt

1. Create 65 random encryption keys and encrypt those keys using gpg. Reading from /dev/random may take indefinitely long if kernel's random entropy pool is empty. If that happens, do some other work on some other console (use keyboard, mouse and disks).

head -c 2925 /dev/random | uuencode -m - | head -n 66 | tail -n 65 \ | gpg --symmetric -a > ~amanda/.gnupg/am_key.gpg

This will ask for a passphrase. Remember this passphrase as you will need it in the next step.

2. Store the passphrase inside the home-directory of the AMANDA-user and protect it with proper permissions:

echo my_secret_passphrase > ~amanda/.am_passphrase
chown amanda:disk ~amanda/.am_passphrase
chmod 700 ~amanda/.am_passphrase

Key and Passphrase

amcrypt uses the same key to encrypt and decrypt data.

It is very important to store and protect the key and the passphrase properly. Encrypted backup data can only be recovered with the correct key and passphrase.


amanda(8), amanda.conf(5), aespipe(1), amaespipe(8), gpg(1)