enc(1ssl)enc(1ssl)NAMEenc - Symmetric cipher routines
SYNOPSIS
openssl enc-ciphername [-in filename] [-out filename] [-pass arg] [-e]
[-d] [-a] [-A] [-k password] [-kfile filename] [-K key] [-ivIV] [-p]
[-P] [-bufsize number] [-debug]
OPTIONS
Input filename, standard input by default. Output filename, standard
output by default. Password source. For more information about the
format of arg see the Pass Phrase Arguments section in openssl(1ssl).
Uses 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. Does not use a salt in the key derivation routines.
This is the default for compatibility with previous versions of OpenSSL
and SSLeay. Encrypts the input data. This is the default. Decrypts
the input data. Base64 processes the data. This means that if encryp‐
tion is taking place the data is base64 encoded after encryption. If
decryption is set then the input data is base64 decoded before being
decrypted. If the -a option is set then base64 processes the data on
one line. The password to derive the key from. This is for compatibil‐
ity with previous versions of OpenSSL. It is superseded by the -pass
argument. Reads the password to derive the key from the first line of
filename. This is for computability with previous versions of OpenSSL.
It is superseded by the -pass argument. The actual salt to use. This
must be represented as a string comprised only of hex digits. The
actual key to use. This must be represented as a string comprised only
of hex digits. If only the key is specified, the IV must also be
specifed using the -iv option. When both a key and password are speci‐
fied, the key given with the -K option will be used, and the IV gener‐
ated from the password will be taken. It probably does not make much
sense to specify both key and password. The actual IV to use. This
must be represented as a string comprised only of hex digits. When
only the key is specified using the -K option, the IV must explicitely
be defined. When a password is specified using one of the other
options, the IV is generated from this password. Prints out the key
and IV used. Prints out the key and IV used then immediately exits.
Does not do any encryption or decryption. Sets the buffer size for I/O
Debugs the BIOs used for I/O.
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.
NOTES
The program can be called either as openssl ciphername or openssl enc-ciphername.
There is a prompt for a password 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
generates 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 generated 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 use a
strong block cipher in CBC mode such as bf or des3.
All the block ciphers use PKCS#5 padding, also known as standard 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 is not a very good test.
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
RESTRICTIONS
The -A option when used with large files does not work properly.
There should be an option to allow an iteration count to be included.
Like the EVP library the enc program only supports a fixed number of
algorithms with certain parameters. For example, if you want to use RC2
with a 76 bit key or RC4 with an 84 bit key you cannot use this pro‐
gram.
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
enc(1ssl)
