amcrypt-ossl-asym(8)

1AMCRYPT-OSSL-ASYM(8)                                      AMCRYPT-OSSL-ASYM(8)
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NAME

6       amcrypt-ossl-asym - crypt program for Amanda asymmetric data encryption
7       using OpenSSL
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SYNOPSIS

10       amcrypt-ossl-asym [-d]
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DESCRIPTION

13       amcrypt-ossl-asym uses OpenSSL to encrypt and decrypt data. OpenSSL is
14       available from www.openssl.org[1]. OpenSSL offers a wide variety of
15       cipher choices ( amcrypt-ossl-asym defaults to 256-bit AES) and can use
16       hardware cryptographic accelerators on several platforms.
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18       amcrypt-ossl-asym will search for the OpenSSL program in the following
19       directories:
20       /bin:/usr/bin:/usr/local/bin:/usr/ssl/bin:/usr/local/ssl/bin.
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GENERATING PUBLIC AND PRIVATE KEYS

23       RSA keys can be generated with the standard OpenSSL commands, e.g.:
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25           $ cd /var/lib/amanda
26           $ openssl genrsa -aes128 -out backup-privkey.pem 1024
27           Generating RSA private key, 1024 bit long modulus
28           [...]
29           Enter pass phrase for backup-privkey.pem: ENTER YOUR PASS PHRASE
30           Verifying - Enter pass phrase for backup-key.pem: ENTER YOUR PASS PHRASE
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32           $ openssl rsa -in backup-privkey.pem -pubout -out backup-pubkey.pem
33           Enter pass phrase for backup-privkey.pem: ENTER YOUR PASS PHRASE
34           Writing RSA key
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37       To generate a private key without a passphrase, omit the -aes128
38       option. See openssl_genrsa(1) for more key generation options.
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40       Note that it is always possible to generate the public key from the
41       private key.
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KEY AND PASSPHRASE MANAGEMENT

44       amcrypt-ossl-asym uses the public key to encrypt data. The security of
45       the data does not depend on the confidentiality of the public key. The
46       private key is used to decrypt data, and must be protected. Encrypted
47       backup data cannot be recovered without the private key. The private
48       key may optionally be encrypted with a passphrase.
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50       While the public key must be online at all times to perorm backups, the
51       private key and optional passphrase are only needed to restore data. It
52       is recommended that the latter be stored offline all other times. For
53       example, you could keep the private key on removable media, and copy it
54       into place for a restore; or you could keep the private key online,
55       encrypted with a passphrase that is present only for a restore.
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57       OpenSSL's key derivation routines use a salt to guard against
58       dictionary attacks on the pass phrase; still it is important to pick a
59       pass phrase that is hard to guess. The Diceware method (see
60       www.diceware.com[2]) can be used to create passphrases that are
61       difficult to guess and easy to remember.
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FILES

64       /var/lib/amanda/backup-privkey.pem
65           File containing the RSA private key. It should not be readable by
66           any user other than the Amanda user.
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68       /var/lib/amanda/backup-pubkey.pem
69           File containing the RSA public key.
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71       /var/lib/amanda/.am_passphrase
72           File containing the passphrase. It should not be readable by any
73           user other than the Amanda user.
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REFERENCES

79        1. www.openssl.org
80           http://www.openssl.org/
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82        2. www.diceware.com
83           http://www.diceware.com/
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87                                  02/07/2007              AMCRYPT-OSSL-ASYM(8)