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ENC(1) OpenSSL ENC(1)
NAME
enc - symmetric cipher routines
SYNOPSIS
openssl enc -ciphername [-in filename] [-out filename] [-pass arg] [-e]
[-d] [-a] [-A] [-k password] [-kfile filename] [-K key] [-iv IV] [-p]
[-P] [-bufsize number] [-nopad] [-debug]
DESCRIPTION
The symmetric cipher commands allow data to be encrypted or decrypted
using various block and stream ciphers using keys based on passwords or
explicitly provided. Base64 encoding or decoding can also be performed
either by itself or in addition to the encryption or decryption.
OPTIONS
-in filename
the input filename, standard input by default.
-out filename
the output filename, standard output by default.
-pass arg
the password source. For more information about the format of arg
see the PASS PHRASE ARGUMENTS section in openssl(1).
-salt
use a salt in the key derivation routines. This option should
ALWAYS be used unless compatibility with previous versions of
OpenSSL or SSLeay is required. This option is only present on
OpenSSL versions 0.9.5 or above.
-nosalt
don't use a salt in the key derivation routines. This is the
default for compatibility with previous versions of OpenSSL and
SSLeay.
-e encrypt the input data: this is the default.
-d decrypt the input data.
-a base64 process the data. This means that if encryption is taking
place the data is base64 encoded after encryption. If decryption is
set then the input data is base64 decoded before being decrypted.
-A if the -a option is set then base64 process the data on one line.
-k password
the password to derive the key from. This is for compatibility with
previous versions of OpenSSL. Superseded by the -pass argument.
-kfile filename
read the password to derive the key from the first line of file-
name. This is for compatibility with previous versions of OpenSSL.
Superseded by the -pass argument.
-S salt
the actual salt to use: this must be represented as a string com-
prised only of hex digits.
-K key
the actual key to use: this must be represented as a string com-
prised only of hex digits. If only the key is specified, the IV
must additionally specified using the -iv option. When both a key
and a password are specified, the key given with the -K option will
be used and the IV generated from the password will be taken. It
probably does not make much sense to specify both key and password.
-iv IV
the actual IV to use: this must be represented as a string com-
prised only of hex digits. When only the key is specified using the
-K option, the IV must explicitly be defined. When a password is
being specified using one of the other options, the IV is generated
from this password.
-p print out the key and IV used.
-P print out the key and IV used then immediately exit: don't do any
encryption or decryption.
-bufsize number
set the buffer size for I/O
-nopad
disable standard block padding
-debug
debug the BIOs used for I/O.
NOTES
The program can be called either as openssl ciphername or openssl enc
-ciphername.
A password will be prompted for to derive the key and IV if necessary.
The -salt option should ALWAYS be used if the key is being derived from
a password unless you want compatibility with previous versions of
OpenSSL and SSLeay.
Without the -salt option it is possible to perform efficient dictionary
attacks on the password and to attack stream cipher encrypted data. The
reason for this is that without the salt the same password always gen-
erates the same encryption key. When the salt is being used the first
eight bytes of the encrypted data are reserved for the salt: it is gen-
erated at random when encrypting a file and read from the encrypted
file when it is decrypted.
Some of the ciphers do not have large keys and others have security
implications if not used correctly. A beginner is advised to just use a
strong block cipher in CBC mode such as bf or des3.
All the block ciphers normally use PKCS#5 padding also known as stan-
dard block padding: this allows a rudimentary integrity or password
check to be performed. However since the chance of random data passing
the test is better than 1 in 256 it isn't a very good test.
If padding is disabled then the input data must be a multiple of the
cipher block length.
All RC2 ciphers have the same key and effective key length.
Blowfish and RC5 algorithms use a 128 bit key.
SUPPORTED CIPHERS
base64 Base 64
bf-cbc Blowfish in CBC mode
bf Alias for bf-cbc
bf-cfb Blowfish in CFB mode
bf-ecb Blowfish in ECB mode
bf-ofb Blowfish in OFB mode
cast-cbc CAST in CBC mode
cast Alias for cast-cbc
cast5-cbc CAST5 in CBC mode
cast5-cfb CAST5 in CFB mode
cast5-ecb CAST5 in ECB mode
cast5-ofb CAST5 in OFB mode
des-cbc DES in CBC mode
des Alias for des-cbc
des-cfb DES in CBC mode
des-ofb DES in OFB mode
des-ecb DES in ECB mode
des-ede-cbc Two key triple DES EDE in CBC mode
des-ede Alias for des-ede
des-ede-cfb Two key triple DES EDE in CFB mode
des-ede-ofb Two key triple DES EDE in OFB mode
des-ede3-cbc Three key triple DES EDE in CBC mode
des-ede3 Alias for des-ede3-cbc
des3 Alias for des-ede3-cbc
des-ede3-cfb Three key triple DES EDE CFB mode
des-ede3-ofb Three key triple DES EDE in OFB mode
desx DESX algorithm.
idea-cbc IDEA algorithm in CBC mode
idea same as idea-cbc
idea-cfb IDEA in CFB mode
idea-ecb IDEA in ECB mode
idea-ofb IDEA in OFB mode
rc2-cbc 128 bit RC2 in CBC mode
rc2 Alias for rc2-cbc
rc2-cfb 128 bit RC2 in CBC mode
rc2-ecb 128 bit RC2 in CBC mode
rc2-ofb 128 bit RC2 in CBC mode
rc2-64-cbc 64 bit RC2 in CBC mode
rc2-40-cbc 40 bit RC2 in CBC mode
rc4 128 bit RC4
rc4-64 64 bit RC4
rc4-40 40 bit RC4
rc5-cbc RC5 cipher in CBC mode
rc5 Alias for rc5-cbc
rc5-cfb RC5 cipher in CBC mode
rc5-ecb RC5 cipher in CBC mode
rc5-ofb RC5 cipher in CBC mode
EXAMPLES
Just base64 encode a binary file:
openssl base64 -in file.bin -out file.b64
Decode the same file
openssl base64 -d -in file.b64 -out file.bin
Encrypt a file using triple DES in CBC mode using a prompted password:
openssl des3 -salt -in file.txt -out file.des3
Decrypt a file using a supplied password:
openssl des3 -d -salt -in file.des3 -out file.txt -k mypassword
Encrypt a file then base64 encode it (so it can be sent via mail for
example) using Blowfish in CBC mode:
openssl bf -a -salt -in file.txt -out file.bf
Base64 decode a file then decrypt it:
openssl bf -d -salt -a -in file.bf -out file.txt
Decrypt some data using a supplied 40 bit RC4 key:
openssl rc4-40 -in file.rc4 -out file.txt -K 0102030405
BUGS
The -A option when used with large files doesn't work properly.
There should be an option to allow an iteration count to be included.
The enc program only supports a fixed number of algorithms with certain
parameters. So if, for example, you want to use RC2 with a 76 bit key
or RC4 with an 84 bit key you can't use this program.
0.9.7d 2005-02-25 ENC(1)
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