Android_verify/third_party/openssl/share/man/man1/openssl-enc.1ossl

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.\" ========================================================================
.\"
.IX Title "OPENSSL-ENC 1ossl"
.TH OPENSSL-ENC 1ossl 2025-01-17 3.4.0 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 \- symmetric cipher routines
.SH SYNOPSIS
.IX Header "SYNOPSIS"
\&\fBopenssl\fR \fBenc\fR|\fIcipher\fR
[\fB\-\fR\f(BIcipher\fR]
[\fB\-help\fR]
[\fB\-list\fR]
[\fB\-ciphers\fR]
[\fB\-in\fR \fIfilename\fR]
[\fB\-out\fR \fIfilename\fR]
[\fB\-pass\fR \fIarg\fR]
[\fB\-e\fR]
[\fB\-d\fR]
[\fB\-a\fR]
[\fB\-base64\fR]
[\fB\-A\fR]
[\fB\-k\fR \fIpassword\fR]
[\fB\-kfile\fR \fIfilename\fR]
[\fB\-K\fR \fIkey\fR]
[\fB\-iv\fR \fIIV\fR]
[\fB\-S\fR \fIsalt\fR]
[\fB\-salt\fR]
[\fB\-nosalt\fR]
[\fB\-z\fR]
[\fB\-md\fR \fIdigest\fR]
[\fB\-iter\fR \fIcount\fR]
[\fB\-pbkdf2\fR]
[\fB\-saltlen\fR \fIsize\fR]
[\fB\-p\fR]
[\fB\-P\fR]
[\fB\-bufsize\fR \fInumber\fR]
[\fB\-nopad\fR]
[\fB\-v\fR]
[\fB\-debug\fR]
[\fB\-none\fR]
[\fB\-engine\fR \fIid\fR]
[\fB\-rand\fR \fIfiles\fR]
[\fB\-writerand\fR \fIfile\fR]
[\fB\-provider\fR \fIname\fR]
[\fB\-provider\-path\fR \fIpath\fR]
[\fB\-propquery\fR \fIpropq\fR]
.PP
\&\fBopenssl\fR \fIcipher\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\-\fR\f(BIcipher\fR 4
.IX Item "-cipher"
The cipher to use.
.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\fR \fIfilename\fR" 4
.IX Item "-in filename"
The input filename, standard input by default.
.IP "\fB\-out\fR \fIfilename\fR" 4
.IX Item "-out filename"
The output filename, standard output by default.
.IP "\fB\-pass\fR \fIarg\fR" 4
.IX Item "-pass arg"
The password source. For more information about the format of \fIarg\fR
see \fBopenssl\-passphrase\-options\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.
.Sp
When the \fB\-A\fR 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.
.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 encoding produces output without any
newline character, and base64 decoding does not require any newlines.
Therefore it can be helpful to use the \fB\-A\fR option when decoding unknown input.
.IP "\fB\-k\fR \fIpassword\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\fR \fIfilename\fR" 4
.IX Item "-kfile filename"
Read the password to derive the key from the first line of \fIfilename\fR.
This is for compatibility with previous versions of OpenSSL. Superseded by
the \fB\-pass\fR argument.
.IP "\fB\-md\fR \fIdigest\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\fR \fIcount\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 PBKDF2 algorithm to derive the key.
.IP \fB\-pbkdf2\fR 4
.IX Item "-pbkdf2"
Use PBKDF2 algorithm with a default iteration count of 10000
unless otherwise specified by the \fB\-iter\fR command line option.
.IP \fB\-saltlen\fR 4
.IX Item "-saltlen"
Set the salt length to use when using the \fB\-pbkdf2\fR option.
For compatibility reasons, the default is 8 bytes.
The maximum value is currently 16 bytes.
If the \fB\-pbkdf2\fR 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.
.IP \fB\-nosalt\fR 4
.IX Item "-nosalt"
Don't use a salt in the key derivation routines. This option \fBSHOULD NOT\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\fR \fIsalt\fR" 4
.IX Item "-S 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 \fB\-saltlen\fR).
.IP "\fB\-K\fR \fIkey\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 IV 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 IV generated from the
password will be taken. It does not make much sense to specify both key
and password.
.IP "\fB\-iv\fR \fIIV\fR" 4
.IX Item "-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 \fB\-K\fR 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.
.IP \fB\-p\fR 4
.IX Item "-p"
Print out the key and IV used.
.IP \fB\-P\fR 4
.IX Item "-P"
Print out the key and IV used then immediately exit: don't do any encryption
or decryption.
.IP "\fB\-bufsize\fR \fInumber\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\-v\fR 4
.IX Item "-v"
Verbose print; display some statistics about I/O and buffer sizes.
.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 NULL cipher (no encryption or decryption of input).
.IP "\fB\-rand\fR \fIfiles\fR, \fB\-writerand\fR \fIfile\fR" 4
.IX Item "-rand files, -writerand file"
See "Random State Options" in \fBopenssl\fR\|(1) for details.
.IP "\fB\-provider\fR \fIname\fR" 4
.IX Item "-provider name"
.PD 0
.IP "\fB\-provider\-path\fR \fIpath\fR" 4
.IX Item "-provider-path path"
.IP "\fB\-propquery\fR \fIpropq\fR" 4
.IX Item "-propquery propq"
.PD
See "Provider Options" in \fBopenssl\fR\|(1), \fBprovider\fR\|(7), and \fBproperty\fR\|(7).
.IP "\fB\-engine\fR \fIid\fR" 4
.IX Item "-engine id"
See "Engine Options" in \fBopenssl\fR\|(1).
This option is deprecated.
.SH NOTES
.IX Header "NOTES"
The program can be called either as \f(CW\*(C`openssl \fR\f(CIcipher\fR\f(CW\*(C'\fR or
\&\f(CW\*(C`openssl enc \-\fR\f(CIcipher\fR\f(CW\*(C'\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 \fBopenssl\-list\fR\|(1) 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 \fB\-engine\fR
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.
.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 IV if necessary.
.PP
The \fB\-salt\fR option should \fBALWAYS\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.
.PP
When the salt is generated at random (that means when encrypting using a
passphrase without explicit salt given using \fB\-S\fR option), the first bytes
of the encrypted data are reserved to store the salt for later decrypting.
.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 AES, in CBC 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 RC2 ciphers have the same key and effective key length.
.PP
Blowfish and RC5 algorithms use a 128 bit key.
.PP
Please note that OpenSSL 3.0 changed the effect of the \fB\-S\fR 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 \fB\-S\fR option is used during decryption, the ciphertext
is expected to not have a prepended salt value.
.PP
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 \fB\-S\fR 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 \fB\-S\fR option, the salt will be then be generated randomly and prepended
to the output.
.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 when invoking this command
with the \fB\-list\fR option (that is \f(CW\*(C`openssl enc \-list\*(C'\fR) is
a list of ciphers, supported by your version of OpenSSL, including
ones provided by configured engines.
.PP
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 \fB\-out\fR 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 \fBopenssl enc\fR 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, \fBopenssl\-cms\fR\|(1) is recommended, as it provides a
standard data format and performs the needed key/iv/nonce management.
.PP
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.
.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
\&
\& 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
.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 AES\-128 using a prompted password
and PBKDF2 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 AES\-256 in CTR mode and PBKDF2 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
.PP
AES key wrapping:
.PP
.Vb 3
\& 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
.Ve
.SH BUGS
.IX Header "BUGS"
The \fB\-A\fR option when used with large files doesn't work properly.
On the other hand, when base64 decoding without the \fB\-A\fR option,
if the first 1024 bytes of input do not include a newline character
the first two lines of input are ignored.
.PP
The \fBopenssl enc\fR 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.
.SH HISTORY
.IX Header "HISTORY"
The default digest was changed from MD5 to SHA256 in OpenSSL 1.1.0.
.PP
The \fB\-list\fR option was added in OpenSSL 1.1.1e.
.PP
The \fB\-ciphers\fR and \fB\-engine\fR options were deprecated in OpenSSL 3.0.
.PP
The \fB\-saltlen\fR option was added in OpenSSL 3.2.
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2000\-2024 The OpenSSL Project Authors. All Rights Reserved.
.PP
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
<https://www.openssl.org/source/license.html>.