/usr/man/cat.1/enc.1
ENC(1) OpenSSL ENC(1)
NAME
openssl-enc, enc - symmetric cipher routines
SYNOPSIS
openssl enc -ciphername [-in filename] [-out filename]
[-pass arg] [-e] [-d] [-a/-base64] [-A] [-k password]
[-kfile filename] [-K key] [-iv IV] [-S salt] [-salt]
[-nosalt] [-z] [-md] [-p] [-P] [-bufsize number] [-nopad]
[-debug] [-none] [-engine id]
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 is the
default.
-nosalt
don't use a salt in the key derivation routines. This
option SHOULD NOT be used except for test purposes or
compatibility with ancient 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.
-base64
same as -a
-A if the -a option is set then base64 process the data on
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ENC(1) OpenSSL ENC(1)
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Superseded by the -pass argument.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 filename. This is for compatibility with previous
versions of OpenSSL. Superseded by the -pass argument.
-nosalt
do not use a salt
-salt
use salt (randomly generated or provide with -S option)
when encrypting (this is the default).
-S salt
the actual salt to use: this must be represented as a
string of hex digits.
-K key
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.
-iv IV
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.
-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
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ENC(1) OpenSSL ENC(1)
-debug
debug the BIOs used for I/O.
-z Compress or decompress clear text using zlib before
encryption or after decryption. This option exists only
if OpenSSL with compiled with zlib or zlib-dynamic
option.
-none
Use NULL cipher (no encryption or decryption of input).
NOTES
The program can be called either as openssl ciphername or
openssl enc -ciphername. But the first form doesn't work
with engine-provided ciphers, because this form is processed
before the configuration file is read and any ENGINEs
loaded.
Engines which provide entirely new encryption algorithms
(such as ccgost engine which provides gost89 algorithm)
should be configured in the configuration file. Engines,
specified in the command line using -engine options can only
be used for hadrware-assisted implementations of ciphers,
which are supported by OpenSSL core or other engine,
specified in the configuration file.
When enc command lists supported ciphers, ciphers provided
by engines, specified in the configuration files are listed
too.
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.
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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 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
Note that some of these ciphers can be disabled at compile
time and some are available only if an appropriate engine is
configured in the configuration file. The output of the enc
command run with unsupported options (for example openssl
enc -help) includes a list of ciphers, supported by your
versesion of OpenSSL, including ones provided by configured
engines.
The enc program does not support authenticated encryption
modes like CCM and GCM. The utility does not store or
retrieve the authentication tag.
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 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
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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
desx DESX algorithm.
gost89 GOST 28147-89 in CFB mode (provided by ccgost engine)
gost89-cnt `GOST 28147-89 in CNT mode (provided by ccgost engine)
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
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
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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.
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See also openssl-enc(1)
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