enc - symmetric cipher routines
B<openssl enc -I<cipher>>
B<openssl> I<[cipher]> [B<...>]
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.
Print out a usage message.
List all supported ciphers.
Alias of -list to display all supported ciphers.
=item B<-in filename>
The input filename, standard input by default.
=item B<-out filename>
The output filename, standard output by default.
=item B<-pass arg>
The password source. For more information about the format of B<arg>
see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
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.
Same as B<-a>
If the B<-a> option is set then base64 process the data on one line.
=item B<-k password>
The password to derive the key from. This is for compatibility with previous
versions of OpenSSL. Superseded by the B<-pass> argument.
=item B<-kfile filename>
Read the password to derive the key from the first line of B<filename>.
This is for compatibility with previous versions of OpenSSL. Superseded by
the B<-pass> argument.
=item B<-md digest>
Use the specified digest to create the key from the passphrase.
The default algorithm is sha-256.
=item B<-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.
Use PBKDF2 algorithm with default iteration count unless otherwise specified.
Don't use a salt in the key derivation routines. This option B<SHOULD NOT> be
used except for test purposes or compatibility with ancient versions of
Use salt (randomly generated or provide with B<-S> option) when
encrypting, this is the default.
=item B<-S salt>
The actual salt to use: this must be represented as a string of hex digits.
=item B<-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 B<-iv> option. When both a key and a password are specified, the
key given with the B<-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
=item B<-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 B<-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
=item B<-bufsize number>
Set the buffer size for I/O.
Disable standard block padding.
Debug the BIOs used for I/O.
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.
Use NULL cipher (no encryption or decryption of input).
=item B<-rand file...>
A file or files containing random data used to seed the random number
Multiple files can be specified separated by an OS-dependent character.
The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
=item [B<-writerand file>]
Writes random data to the specified I<file> upon exit.
This can be used with a subsequent B<-rand> flag.
The program can be called either as B<openssl cipher> or
B<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 B<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 B<-salt> option should B<ALWAYS> be used if the key is being derived
from a password unless you want compatibility with previous versions of
Without the B<-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
All RC2 ciphers have the same key and effective key length.
Blowfish and RC5 algorithms use a 128 bit key.
=head1 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 B<enc> command run with
the B<-ciphers> option (that is B<openssl enc -ciphers>) produces a
list of ciphers, supported by your version of OpenSSL, including
ones provided by configured engines.
The B<enc> program does not support authenticated encryption modes
like CCM and GCM, and will not support such modes in the future.
The B<enc> interface by necessity must begin streaming output (e.g.,
to standard output when B<-out> is not used) before the authentication
tag could be validated, leading to the usage of B<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 B<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 B<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, L<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
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 \
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 \
The B<-A> option when used with large files doesn't work properly.
The B<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.
The default digest was changed from MD5 to SHA256 in OpenSSL 1.1.0.
The B<-list> option was added in OpenSSL 1.1.1e.
Copyright 2000-2020 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