enc
ENC(1SSL) OpenSSL ENC(1SSL)
NAME
openssl-enc, enc - symmetric cipher routines
SYNOPSIS
openssl enc -cipher [-help] [-list] [-ciphers] [-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 digest] [-iter count] [-pbkdf2] [-p] [-P] [-bufsize number]
[-nopad] [-debug] [-none] [-rand file...] [-writerand file] [-engine
id]
openssl [cipher] [...]
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
-help
Print out a usage message.
-list
List all supported ciphers.
-ciphers
Alias of -list to display all supported ciphers.
-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).
-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 Superseded by the -pass argument.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 Superseded by the -pass argument.
-md digest
Use the specified digest to create the key from the passphrase.
The default algorithm is sha-256.
-iter count
Use a given number of iterations on the password in deriving the
encryption key. High values increase the time required to brute-
force the resulting file. This option enables the use of PBKDF2
algorithm to derive the key.
-pbkdf2
Use PBKDF2 algorithm with default iteration count unless otherwise
specified.
-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.
-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
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).
-rand file...
A file or files containing random data used to seed the random
number generator. Multiple files can be specified separated by an
OS-dependent character. The separator is ; for MS-Windows, , for
OpenVMS, and : for all others.
[-writerand file]
Writes random data to the specified file upon exit. This can be
used with a subsequent -rand flag.
NOTES
The program can be called either as openssl cipher or openssl enc
-cipher. 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. Use the list command to get a list of
supported ciphers.
Engines which provide entirely new encryption algorithms (such as the
ccgost engine which provides gost89 algorithm) should be configured in
the configuration file. Engines specified on the command line using
-engine options can only be used for hardware-assisted implementations
of ciphers which are supported by the OpenSSL core or another engine
specified in the configuration file.
When the 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.
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, such as AES, in CBC mode.
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 the -ciphers
option (that is openssl enc -ciphers) produces a list of ciphers,
supported by your version of OpenSSL, including ones provided by
configured engines.
The enc program does not support authenticated encryption modes like
CCM and GCM, and will not support such modes in the future. The enc
interface by necessity must begin streaming output (e.g., to standard
output when -out is not used) before the authentication tag could be
validated, leading to the usage of enc in pipelines that begin
processing untrusted data and are not capable of rolling back upon
authentication failure. The AEAD modes currently in common use also
suffer from catastrophic failure of confidentiality and/or integrity
upon reuse of key/iv/nonce, and since enc places the entire burden of
key/iv/nonce management upon the user, the risk of exposing AEAD modes
is too great to allow. These key/iv/nonce management issues also
affect other modes currently exposed in enc, but the failure modes are
less extreme in these cases, and the functionality cannot be removed
with a stable release branch. For bulk encryption of data, whether
using authenticated encryption modes or other modes, cms(1) is
recommended, as it provides a standard data format and performs the
needed key/iv/nonce management.
base64 Base 64
bf-cbc Blowfish in CBC mode
bf Alias for bf-cbc
blowfish 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
chacha20 ChaCha20 algorithm
des-cbc DES in CBC mode
des Alias for des-cbc
des-cfb DES in CFB 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
seed-cbc SEED cipher in CBC mode
seed Alias for seed-cbc
seed-cfb SEED cipher in CFB mode
seed-ecb SEED cipher in ECB mode
seed-ofb SEED cipher in OFB mode
sm4-cbc SM4 cipher in CBC mode
sm4 Alias for sm4-cbc
sm4-cfb SM4 cipher in CFB mode
sm4-ctr SM4 cipher in CTR mode
sm4-ecb SM4 cipher in ECB mode
sm4-ofb SM4 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]-ctr 128/192/256 bit AES in CTR 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
aria-[128|192|256]-cbc 128/192/256 bit ARIA in CBC mode
aria[128|192|256] Alias for aria-[128|192|256]-cbc
aria-[128|192|256]-cfb 128/192/256 bit ARIA in 128 bit CFB mode
aria-[128|192|256]-cfb1 128/192/256 bit ARIA in 1 bit CFB mode
aria-[128|192|256]-cfb8 128/192/256 bit ARIA in 8 bit CFB mode
aria-[128|192|256]-ctr 128/192/256 bit ARIA in CTR mode
aria-[128|192|256]-ecb 128/192/256 bit ARIA in ECB mode
aria-[128|192|256]-ofb 128/192/256 bit ARIA in OFB mode
camellia-[128|192|256]-cbc 128/192/256 bit Camellia in CBC mode
camellia[128|192|256] Alias for camellia-[128|192|256]-cbc
camellia-[128|192|256]-cfb 128/192/256 bit Camellia in 128 bit CFB mode
camellia-[128|192|256]-cfb1 128/192/256 bit Camellia in 1 bit CFB mode
camellia-[128|192|256]-cfb8 128/192/256 bit Camellia in 8 bit CFB mode
camellia-[128|192|256]-ctr 128/192/256 bit Camellia in CTR mode
camellia-[128|192|256]-ecb 128/192/256 bit Camellia in ECB mode
camellia-[128|192|256]-ofb 128/192/256 bit Camellia 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 AES-128 using a prompted password and PBKDF2 key
derivation:
openssl enc -aes128 -pbkdf2 -in file.txt -out file.aes128
Decrypt a file using a supplied password:
openssl enc -aes128 -pbkdf2 -d -in file.aes128 -out file.txt \
-pass pass:<password>
Encrypt a file then base64 encode it (so it can be sent via mail for
example) using AES-256 in CTR mode and PBKDF2 key derivation:
openssl enc -aes-256-ctr -pbkdf2 -a -in file.txt -out file.aes256
Base64 decode a file then decrypt it using a password supplied in a
file:
openssl enc -aes-256-ctr -pbkdf2 -d -a -in file.aes256 -out file.txt \
-pass file:<passfile>
BUGS
The -A option when used with large files doesn't work properly.
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.
HISTORY
The default digest was changed from MD5 to SHA256 in OpenSSL 1.1.0.
The -list option was added in OpenSSL 1.1.1e.
COPYRIGHT
Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
1.1.1f 2023-10-10 ENC(1SSL)
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