enc — symmetric cipher routines
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]
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
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
don't use a salt in the key derivation routines. This is the
default for compatibility with previous versions of OpenSSL and
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
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 Superseded by the -pass argument.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 computability 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Superseded by the -pass argument.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: don't
do any encryption or decryption.
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
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 isn't a very good
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.
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
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
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 doesn't work properly.
There should be an option to allow an iteration count to be
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.