openssl-enc, enc - symmetric cipher routines
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] [...]
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
- Print out a usage message.
- List all supported 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 "Pass Phrase Options" in 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 -a
- If the -a option is set then base64 process the data on one
- -k password
- The password to derive the key from. This is for compatibility with
previous versions of OpenSSL. Superseded by the -pass
- 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 Superseded by the -pass argument.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
- Use PBKDF2 algorithm with default iteration count unless otherwise
- 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.
- 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
- -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
- 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.
- Compress or decompress encrypted data using zlib after encryption or
before decryption. This option exists only if OpenSSL was compiled with
the zlib or zlib-dynamic option.
- 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.
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
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
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
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.
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
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
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
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
openssl enc -aes-256-ctr -pbkdf2 -d -a -in file.aes256 -out file.txt \
The -A option when used with large files doesn't work
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.
The default digest was changed from MD5 to SHA256 in OpenSSL
The -list option was added in OpenSSL 1.1.1e.
Copyright 2000-2021 The OpenSSL Project Authors. All Rights
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