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.\" ========================================================================
.\"
.IX Title "ENC 1"
.TH ENC 1 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
openssl\-enc, enc \- symmetric cipher routines
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
\&\fBopenssl enc \-\f(BIcipher\fB\fR
[\fB\-help\fR]
[\fB\-list\fR]
[\fB\-ciphers\fR]
[\fB\-in filename\fR]
[\fB\-out filename\fR]
[\fB\-pass arg\fR]
[\fB\-e\fR]
[\fB\-d\fR]
[\fB\-a\fR]
[\fB\-base64\fR]
[\fB\-A\fR]
[\fB\-k password\fR]
[\fB\-kfile filename\fR]
[\fB\-K key\fR]
[\fB\-iv \s-1IV\s0\fR]
[\fB\-S salt\fR]
[\fB\-salt\fR]
[\fB\-nosalt\fR]
[\fB\-z\fR]
[\fB\-md digest\fR]
[\fB\-iter count\fR]
[\fB\-pbkdf2\fR]
[\fB\-p\fR]
[\fB\-P\fR]
[\fB\-bufsize number\fR]
[\fB\-nopad\fR]
[\fB\-debug\fR]
[\fB\-none\fR]
[\fB\-rand file...\fR]
[\fB\-writerand file\fR]
[\fB\-engine id\fR]
.PP
\&\fBopenssl\fR \fI[cipher]\fR [\fB...\fR]
.SH "DESCRIPTION"
.IX Header "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.
.SH "OPTIONS"
.IX Header "OPTIONS"
.IP "\fB\-help\fR" 4
.IX Item "-help"
Print out a usage message.
.IP "\fB\-list\fR" 4
.IX Item "-list"
List all supported ciphers.
.IP "\fB\-ciphers\fR" 4
.IX Item "-ciphers"
Alias of \-list to display all supported ciphers.
.IP "\fB\-in filename\fR" 4
.IX Item "-in filename"
The input filename, standard input by default.
.IP "\fB\-out filename\fR" 4
.IX Item "-out filename"
The output filename, standard output by default.
.IP "\fB\-pass arg\fR" 4
.IX Item "-pass arg"
The password source. For more information about the format of \fBarg\fR
see \*(L"Pass Phrase Options\*(R" in \fBopenssl\fR\|(1).
.IP "\fB\-e\fR" 4
.IX Item "-e"
Encrypt the input data: this is the default.
.IP "\fB\-d\fR" 4
.IX Item "-d"
Decrypt the input data.
.IP "\fB\-a\fR" 4
.IX Item "-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.
.IP "\fB\-base64\fR" 4
.IX Item "-base64"
Same as \fB\-a\fR
.IP "\fB\-A\fR" 4
.IX Item "-A"
If the \fB\-a\fR option is set then base64 process the data on one line.
.IP "\fB\-k password\fR" 4
.IX Item "-k password"
The password to derive the key from. This is for compatibility with previous
versions of OpenSSL. Superseded by the \fB\-pass\fR argument.
.IP "\fB\-kfile filename\fR" 4
.IX Item "-kfile filename"
Read the password to derive the key from the first line of \fBfilename\fR.
This is for compatibility with previous versions of OpenSSL. Superseded by
the \fB\-pass\fR argument.
.IP "\fB\-md digest\fR" 4
.IX Item "-md digest"
Use the specified digest to create the key from the passphrase.
The default algorithm is sha\-256.
.IP "\fB\-iter count\fR" 4
.IX Item "-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 \s-1PBKDF2\s0 algorithm to derive the key.
.IP "\fB\-pbkdf2\fR" 4
.IX Item "-pbkdf2"
Use \s-1PBKDF2\s0 algorithm with default iteration count unless otherwise specified.
.IP "\fB\-nosalt\fR" 4
.IX Item "-nosalt"
Don't use a salt in the key derivation routines. This option \fB\s-1SHOULD NOT\s0\fR be
used except for test purposes or compatibility with ancient versions of
OpenSSL.
.IP "\fB\-salt\fR" 4
.IX Item "-salt"
Use salt (randomly generated or provide with \fB\-S\fR option) when
encrypting, this is the default.
.IP "\fB\-S salt\fR" 4
.IX Item "-S salt"
The actual salt to use: this must be represented as a string of hex digits.
.IP "\fB\-K key\fR" 4
.IX Item "-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 \s-1IV\s0 must additionally specified
using the \fB\-iv\fR option. When both a key and a password are specified, the
key given with the \fB\-K\fR option will be used and the \s-1IV\s0 generated from the
password will be taken. It does not make much sense to specify both key
and password.
.IP "\fB\-iv \s-1IV\s0\fR" 4
.IX Item "-iv IV"
The actual \s-1IV\s0 to use: this must be represented as a string comprised only
of hex digits. When only the key is specified using the \fB\-K\fR option, the
\&\s-1IV\s0 must explicitly be defined. When a password is being specified using
one of the other options, the \s-1IV\s0 is generated from this password.
.IP "\fB\-p\fR" 4
.IX Item "-p"
Print out the key and \s-1IV\s0 used.
.IP "\fB\-P\fR" 4
.IX Item "-P"
Print out the key and \s-1IV\s0 used then immediately exit: don't do any encryption
or decryption.
.IP "\fB\-bufsize number\fR" 4
.IX Item "-bufsize number"
Set the buffer size for I/O.
.IP "\fB\-nopad\fR" 4
.IX Item "-nopad"
Disable standard block padding.
.IP "\fB\-debug\fR" 4
.IX Item "-debug"
Debug the BIOs used for I/O.
.IP "\fB\-z\fR" 4
.IX Item "-z"
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.
.IP "\fB\-none\fR" 4
.IX Item "-none"
Use \s-1NULL\s0 cipher (no encryption or decryption of input).
.IP "\fB\-rand file...\fR" 4
.IX Item "-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 \fB;\fR for MS-Windows, \fB,\fR for OpenVMS, and \fB:\fR for
all others.
.IP "[\fB\-writerand file\fR]" 4
.IX Item "[-writerand file]"
Writes random data to the specified \fIfile\fR upon exit.
This can be used with a subsequent \fB\-rand\fR flag.
.SH "NOTES"
.IX Header "NOTES"
The program can be called either as \fBopenssl cipher\fR or
\&\fBopenssl enc \-cipher\fR. 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 \fBlist\fR command to get a list of supported ciphers.
.PP
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.
.PP
When the enc command lists supported ciphers, ciphers provided by engines,
specified in the configuration files are listed too.
.PP
A password will be prompted for to derive the key and \s-1IV\s0 if necessary.
.PP
The \fB\-salt\fR option should \fB\s-1ALWAYS\s0\fR be used if the key is being derived
from a password unless you want compatibility with previous versions of
OpenSSL.
.PP
Without the \fB\-salt\fR 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.
.PP
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 \s-1AES,\s0 in \s-1CBC\s0 mode.
.PP
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.
.PP
If padding is disabled then the input data must be a multiple of the cipher
block length.
.PP
All \s-1RC2\s0 ciphers have the same key and effective key length.
.PP
Blowfish and \s-1RC5\s0 algorithms use a 128 bit key.
.SH "SUPPORTED CIPHERS"
.IX Header "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 \fBenc\fR command run with
the \fB\-ciphers\fR option (that is \fBopenssl enc \-ciphers\fR) produces a
list of ciphers, supported by your version of OpenSSL, including
ones provided by configured engines.
.PP
The \fBenc\fR program does not support authenticated encryption modes
like \s-1CCM\s0 and \s-1GCM,\s0 and will not support such modes in the future.
The \fBenc\fR interface by necessity must begin streaming output (e.g.,
to standard output when \fB\-out\fR is not used) before the authentication
tag could be validated, leading to the usage of \fBenc\fR in pipelines
that begin processing untrusted data and are not capable of rolling
back upon authentication failure. The \s-1AEAD\s0 modes currently in common
use also suffer from catastrophic failure of confidentiality and/or
integrity upon reuse of key/iv/nonce, and since \fBenc\fR places the
entire burden of key/iv/nonce management upon the user, the risk of
exposing \s-1AEAD\s0 modes is too great to allow. These key/iv/nonce
management issues also affect other modes currently exposed in \fBenc\fR,
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, \fBcms\fR\|(1) is recommended, as it provides a
standard data format and performs the needed key/iv/nonce management.
.PP
.Vb 1
\& 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
.Ve
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Just base64 encode a binary file:
.PP
.Vb 1
\& openssl base64 \-in file.bin \-out file.b64
.Ve
.PP
Decode the same file
.PP
.Vb 1
\& openssl base64 \-d \-in file.b64 \-out file.bin
.Ve
.PP
Encrypt a file using \s-1AES\-128\s0 using a prompted password
and \s-1PBKDF2\s0 key derivation:
.PP
.Vb 1
\& openssl enc \-aes128 \-pbkdf2 \-in file.txt \-out file.aes128
.Ve
.PP
Decrypt a file using a supplied password:
.PP
.Vb 2
\& openssl enc \-aes128 \-pbkdf2 \-d \-in file.aes128 \-out file.txt \e
\& \-pass pass:<password>
.Ve
.PP
Encrypt a file then base64 encode it (so it can be sent via mail for example)
using \s-1AES\-256\s0 in \s-1CTR\s0 mode and \s-1PBKDF2\s0 key derivation:
.PP
.Vb 1
\& openssl enc \-aes\-256\-ctr \-pbkdf2 \-a \-in file.txt \-out file.aes256
.Ve
.PP
Base64 decode a file then decrypt it using a password supplied in a file:
.PP
.Vb 2
\& openssl enc \-aes\-256\-ctr \-pbkdf2 \-d \-a \-in file.aes256 \-out file.txt \e
\& \-pass file:<passfile>
.Ve
.SH "BUGS"
.IX Header "BUGS"
The \fB\-A\fR option when used with large files doesn't work properly.
.PP
The \fBenc\fR program only supports a fixed number of algorithms with
certain parameters. So if, for example, you want to use \s-1RC2\s0 with a
76 bit key or \s-1RC4\s0 with an 84 bit key you can't use this program.
.SH "HISTORY"
.IX Header "HISTORY"
The default digest was changed from \s-1MD5\s0 to \s-1SHA256\s0 in OpenSSL 1.1.0.
.PP
The \fB\-list\fR option was added in OpenSSL 1.1.1e.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2021 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.