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Manual: openssl-enc

OPENSSL-ENC(1SSL) OpenSSL OPENSSL-ENC(1SSL)

NAME
openssl-enc - symmetric cipher routines

SYNOPSIS
openssl enc|cipher [-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] [-saltlen size] [-p] [-P] [-bufsize number] [-nopad] [-v] [-debug] [-none] [-skeymgmt skeymgmt]
[-skeyopt opt:value] [-engine id] [-rand files] [-writerand file] [-provider name] [-provider-path path] [-provparam
[name:]key=value] [-propquery propq]

openssl cipher [...]

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.

OPTIONS
-cipher
The cipher to use.

-help
Print out a usage message.

-list
List all supported ciphers.

-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 openssl-passphrase-options(1).

-e Encrypt the input data: this is the default.

-d Decrypt the input data.

-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 -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.

-base64
Same as -a

-A If the -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 -A option when decoding unknown input.

-k password
The password to derive the key from. This is for compatibility with previous versions of OpenSSL. Superseded by
the -pass argument.

-kfile filename
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 Superseded by the -pass argument.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 the key.

-pbkdf2
Use PBKDF2 algorithm with a default iteration count of 10000 unless otherwise specified by the -iter command line
option.

-saltlen
Set the salt length to use when using the -pbkdf2 option. For compatibility reasons, the default is 8 bytes.
The maximum value is currently 16 bytes. If the -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.

-nosalt
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.

-salt
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 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 -saltlen).

-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 password.

-p Print out the key and IV used.

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

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

-nopad
Disable standard block padding.

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

-debug
Debug the BIOs used for I/O.

-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.

-none
Use NULL cipher (no encryption or decryption of input).

-skeymgmt skeymgmt
Some providers may support opaque symmetric keys objects. To use them, we need to know the name of the
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 "openssl list
-skey-managers" command.

-skeyopt opt: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.

-rand files, -writerand file
See "Random State Options" in openssl(1) for details.

-provider name
-provider-path path
-provparam [name:]key=value
-propquery propq
See "Provider Options" in openssl(1), provider(7), and property(7).

-engine id
See "Engine Options" in openssl(1). This option is deprecated.

NOTES
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 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 -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 -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 generated at random (that means when encrypting using a passphrase without explicit salt given using
-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 -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 -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 -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 -S option, the salt will be then be generated randomly and prepended to the output.

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 -list option (that is
"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 -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 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, 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

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:

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:

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

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

The 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.

Manual: openssl-enc

Related Commands: