=pod
{- OpenSSL::safe::output_do_not_edit_headers(); -}

=head1 NAME

openssl-enc - symmetric cipher routines

=head1 SYNOPSIS

B<openssl> B<enc>|I<cipher>
[B<-I<cipher>>]
[B<-help>]
[B<-list>]
[B<-ciphers>]
[B<-in> I<filename>]
[B<-out> I<filename>]
[B<-pass> I<arg>]
[B<-e>]
[B<-d>]
[B<-a>]
[B<-base64>]
[B<-A>]
[B<-k> I<password>]
[B<-kfile> I<filename>]
[B<-K> I<key>]
[B<-iv> I<IV>]
[B<-S> I<salt>]
[B<-salt>]
[B<-nosalt>]
[B<-z>]
[B<-md> I<digest>]
[B<-iter> I<count>]
[B<-pbkdf2>]
[B<-saltlen> I<size>]
[B<-p>]
[B<-P>]
[B<-bufsize> I<number>]
[B<-nopad>]
[B<-v>]
[B<-debug>]
[B<-none>]
[B<-skeymgmt> I<skeymgmt>]
[B<-skeyopt> I<opt>:I<value>]
{- $OpenSSL::safe::opt_engine_synopsis -}{- $OpenSSL::safe::opt_r_synopsis -}
{- $OpenSSL::safe::opt_provider_synopsis -}

B<openssl> I<cipher> [B<...>]

=head1 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.

=head1 OPTIONS

=over 4

=item B<-I<cipher>>

The cipher to use.

=item B<-help>

Print out a usage message.

=item B<-list>

List all supported ciphers.

=item B<-ciphers>

Alias of -list to display all supported ciphers.

=item B<-in> I<filename>

The input filename, standard input by default.

=item B<-out> I<filename>

The output filename, standard output by default.

=item B<-pass> I<arg>

The password source. For more information about the format of I<arg>
see L<openssl-passphrase-options(1)>.

=item B<-e>

Encrypt the input data: this is the default.

=item B<-d>

Decrypt the input data.

=item B<-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.

When the B<-A> option not given,
on encoding a newline is inserted after each 64 characters, and
on decoding a newline is expected among the first 1024 bytes of input.

=item B<-base64>

Same as B<-a>

=item B<-A>

If the B<-a> option is set then base64 encoding produces output without any
newline character, and base64 decoding does not require any newlines.
Therefore it can be helpful to use the B<-A> option when decoding unknown input.

=item B<-k> I<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 Superseded by the B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> I<filename>

Read the password to derive the key from the first line of I<filename>.
This is for compatibility with previous versions of OpenSSL. Superseded by
the B<-pass> argument.

=item B<-md> I<digest>

Use the specified digest to create the key from the passphrase.
The default algorithm is sha-256.

=item B<-iter> I<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.

=item B<-pbkdf2>

Use PBKDF2 algorithm with a default iteration count of 10000
unless otherwise specified by the B<-iter> command line option.

=item B<-saltlen>

Set the salt length to use when using the B<-pbkdf2> option.
For compatibility reasons, the default is 8 bytes.
The maximum value is currently 16 bytes.
If the B<-pbkdf2> option is not used, then this option is ignored
and a fixed salt length of 8 is used. The salt length used when
encrypting must also be used when decrypting.

=item B<-nosalt>

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
OpenSSL.

=item B<-salt>

Use salt (randomly generated or provide with B<-S> option) when
encrypting, this is the default.

=item B<-S> I<salt>

The actual salt to use: this must be represented as a string of hex digits.
If this option is used while encrypting, the same exact value will be needed
again during decryption. This salt may be truncated or zero padded to
match the salt length (See B<-saltlen>).

=item B<-K> I<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
and password.

=item B<-iv> I<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.

=item B<-p>

Print out the key and IV used.

=item B<-P>

Print out the key and IV used then immediately exit: don't do any encryption
or decryption.

=item B<-bufsize> I<number>[B<k>]

Set the buffer size for I/O.
The maximum size that can be specified is B<2^31-1> (2147483647) bytes.
The B<k> suffix can be specified to indicate that I<number> is provided
in kibibytes (multiples of 1024 bytes).

=item B<-nopad>

Disable standard block padding.

=item B<-v>

Verbose print; display some statistics about I/O and buffer sizes.

=item B<-debug>

Debug the BIOs used for I/O.

=item B<-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.

=item B<-none>

Use NULL cipher (no encryption or decryption of input).

=item B<-skeymgmt> I<skeymgmt>

Some providers may support opaque symmetric keys objects. To use them, we need
to know the name of the B<EVP_SKEYMGMT> to be used. If not specified, the name
of the cipher will be used.

To find out the name of the suitable symmetric key management,
please refer to the output of the C<openssl list -skey-managers> command.

=item B<-skeyopt> I<opt>:I<value>

To obtain an existing opaque symmetric key or generate a new one, key
options are specified as opt:value. These options can't be used together with
any options implying raw key directly or indirectly.

{- $OpenSSL::safe::opt_r_item -}

{- $OpenSSL::safe::opt_provider_item -}

{- $OpenSSL::safe::opt_engine_item -}

=back

=head1 NOTES

The program can be called either as C<openssl I<cipher>> or
C<openssl enc -I<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 L<openssl-list(1)> 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 B<-engine>
option 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
OpenSSL.

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 generated at random (that means when encrypting using a
passphrase without explicit salt given using B<-S> option), the first bytes
of the encrypted data are reserved to store the salt for later decrypting.

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#7 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.

Please note that OpenSSL 3.0 changed the effect of the B<-S> option.
Any explicit salt value specified via this option is no longer prepended to the
ciphertext when encrypting, and must again be explicitly provided when decrypting.
Conversely, when the B<-S> option is used during decryption, the ciphertext
is expected to not have a prepended salt value.

When using OpenSSL 3.0 or later to decrypt data that was encrypted with an
explicit salt under OpenSSL 1.1.1 do not use the B<-S> option, the salt will
then be read from the ciphertext.
To generate ciphertext that can be decrypted with OpenSSL 1.1.1 do not use
the B<-S> option, the salt will be then be generated randomly and prepended
to the output.

=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 when invoking this command
with the B<-list> option (that is C<openssl enc -list>) is
a list of ciphers, supported by your version of OpenSSL, including
ones provided by configured engines.

This command does not support authenticated encryption modes
like CCM and GCM, and will not support such modes in the future.
This is due to having to begin streaming output (e.g., to standard output
when B<-out> is not used) before the authentication tag could be validated.
When this command is used in a pipeline, the receiving end will not be
able to roll 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<openssl 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 this command,
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<openssl-cms(1)> is recommended, as it provides a
standard data format and performs the needed key/iv/nonce management.

When enc is used with key wrapping modes the input data cannot be streamed,
meaning it must be processed in a single pass.
Consequently, the input data size must be less than
the buffer size (-bufsize arg, default to 8*1024 bytes).
The '*-wrap' ciphers require the input to be a multiple of 8 bytes long,
because no padding is involved.
The '*-wrap-pad' ciphers allow any input length.
In both cases, no IV is needed. See example below.


 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

 aes-[128|192|256]-wrap     key wrapping using 128/192/256 bit AES
 aes-[128|192|256]-wrap-pad key wrapping with padding using 128/192/256 bit AES

 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

=head1 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>

AES key wrapping:

 openssl enc -e -a -id-aes128-wrap-pad -K 000102030405060708090A0B0C0D0E0F -in file.bin
or
 openssl aes128-wrap-pad -e -a -K 000102030405060708090A0B0C0D0E0F -in file.bin

=head1 BUGS

The B<-A> option when used with large files doesn't work properly.
On the other hand, when base64 decoding without the B<-A> option,
if the first 1024 bytes of input do not include a newline character
the first two lines of input are ignored.

The B<openssl enc> command 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.

=head1 SEE ALSO

L<openssl-list(1)>, L<EVP_SKEY(3)>

=head1 HISTORY

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.

The B<-ciphers> and B<-engine> options were deprecated in OpenSSL 3.0.

The B<-saltlen> option was added in OpenSSL 3.2.

The B<-skeymgmt> and B<-skeyopt> options were added in OpenSSL 3.5.

=head1 COPYRIGHT

Copyright 2000-2025 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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
L<https://www.openssl.org/source/license.html>.

=cut
