NAME
amcrypt-ossl-asym - crypt program for Amanda asymmetric data encryption
using OpenSSL
SYNOPSIS
amcrypt-ossl-asym [-d]
DESCRIPTION
amcrypt-ossl-asym uses OpenSSL to encrypt and decrypt data. OpenSSL is
available from www.openssl.org. OpenSSL offers a wide variety of cipher
choices ( amcrypt-ossl-asym defaults to 256-bit AES) and can use
hardware cryptographic accelerators on several platforms.
amcrypt-ossl-asym will search for the OpenSSL program in the following
directories:
/bin:/usr/bin:/usr/local/bin:/usr/ssl/bin:/usr/local/ssl/bin.
GENERATING PUBLIC AND PRIVATE KEYS
RSA keys can be generated with the standard OpenSSL commands, e.g.:
$ cd /var/lib/amanda
$ openssl genrsa -aes128 -out backup-privkey.pem 1024
Generating RSA private key, 1024 bit long modulus
[...]
Enter pass phrase for backup-privkey.pem: ENTER YOUR PASS PHRASE
Verifying - Enter pass phrase for backup-key.pem: ENTER YOUR PASS PHRASE
$ openssl rsa -in backup-privkey.pem -pubout -out backup-pubkey.pem
Enter pass phrase for backup-privkey.pem: ENTER YOUR PASS PHRASE
Writing RSA key
To generate a private key without a passphrase, omit the -aes128
option. See openssl_genrsa(1) for more key generation options.
Note that it is always possible to generate the public key from the
private key.
KEY AND PASSPHRASE MANAGEMENT
amcrypt-ossl-asym uses the public key to encrypt data. The security of
the data does not depend on the confidentiality of the public key. The
private key is used to decrypt data, and must be protected. Encrypted
backup data cannot be recovered without the private key. The private
key may optionally be encrypted with a passphrase.
While the public key must be online at all times to perorm backups, the
private key and optional passphrase are only needed to restore data. It
is recommended that the latter be stored offline all other times. For
example, you could keep the private key on removable media, and copy it
into place for a restore; or you could keep the private key online,
encrypted with a passphrase that is present only for a restore.
OpenSSL´s key derivation routines use a salt to guard against
dictionary attacks on the pass phrase; still it is important to pick a
pass phrase that is hard to guess. The Diceware method (see
www.diceware.com) can be used to create passphrases that are difficult
to guess and easy to remember.
FILES
/var/lib/amanda/backup-privkey.pem
File containing the RSA private key. It should not be readable by
any user other than the Amanda user.
/var/lib/amanda/backup-pubkey.pem
File containing the RSA public key.
/var/lib/amanda/.am_passphrase
File containing the passphrase. It should not be readable by any
user other than the Amanda user.
SEE ALSO
amanda(8), amanda.conf(5), openssl(1), amcrypt-ossl(8)
The Amanda Wiki: : http://wiki.zmanda.com/
AUTHOR
Kevin Till <kevin.till@zmanda.com>
Zmanda, Inc. (http://www.zmanda.com)
NOTES
1. www.openssl.org
http://www.openssl.org/
2. www.diceware.com
http://www.diceware.com/