- Unix, Linux Command
enc - symmetric cipher routines
openssl enc -ciphername
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.
the input filename, standard input by default.
the output filename, standard output by default.
the password source. For more information about the format of arg
see the PASS PHRASE ARGUMENTS section in openssl(1).
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
dont use a salt in the key derivation routines. This is the default for
compatibility with previous versions of OpenSSL and SSLeay.
encrypt the input data: this is the default.
decrypt the input data.
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.
if the -a option is set then base64 process the data on one line.
the password to derive the key from. This is for compatibility with previous
versions of OpenSSL. Superseded by the -pass argument.
read the password to derive the key from the first line of filename.
This is for compatibility with previous versions of OpenSSL. Superseded by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 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.
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 explicitly be defined. When a password is being specified using
one of the other options, the IV is generated from this password.
print out the key and IV used.
print out the key and IV used then immediately exit: dont do any encryption
set the buffer size for I/O
disable standard block padding
debug the BIOs used for I/O.
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 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 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 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 isnt a very good test.
If padding is disabled then the input data must be a multiple of the cipher
All RC2 ciphers have the same key and effective key length.
Blowfish and RC5 algorithms use a 128 bit key.
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 Two key triple DES EDE in ECB mode
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 Three key triple DES EDE in ECB mode
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
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 CFB mode
rc2-ecb 128 bit RC2 in ECB mode
rc2-ofb 128 bit RC2 in OFB 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 CFB mode
rc5-ecb RC5 cipher in ECB mode
rc5-ofb RC5 cipher in OFB mode
aes-[128|192|256]-cbc 128/192/256 bit AES in CBC mode
aes-[128|192|256] Alias for aes-[128|192|256]-cbc
aes-[128|192|256]-cfb 128/192/256 bit AES in 128 bit CFB mode
aes-[128|192|256]-cfb1 128/192/256 bit AES in 1 bit CFB mode
aes-[128|192|256]-cfb8 128/192/256 bit AES in 8 bit CFB mode
aes-[128|192|256]-ecb 128/192/256 bit AES in ECB mode
aes-[128|192|256]-ofb 128/192/256 bit AES in OFB mode
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
The -A option when used with large files doesnt 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 cant use this program.