ENC
Section: OpenSSL (1)
Updated: 2017-05-25
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NAME
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 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 Superseded by the -pass argument.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 Superseded by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
- -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.
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
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
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.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- NOTES
-
- SUPPORTED CIPHERS
-
- EXAMPLES
-
- BUGS
-
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