man > openssl-enc(1)

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] [-p] [-P] [-bufsize number]
       [-nopad] [-v] [-debug] [-none] [-engine id] [-rand files] [-writerand file] [-provider name]
       [-provider-path path] [-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.

       -base64
           Same as -a

       -A  If the -a option is set then base64 process the data on one line.

       -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 Superseded by the -pass argument.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 Superseded by the -pass argument.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.

       -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.

       -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
           Set the buffer size for I/O.

       -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).

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

       -provider name
       -provider-path path
       -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#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.

       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.

        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

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>

BUGS
       The -A option when used with large files doesn't work properly.

       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.

HISTORY
       The default digest was changed from MD5 to SHA256 in OpenSSL 1.1.0.

       The -list option was added in OpenSSL 1.1.1e.

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

COPYRIGHT
       Copyright 2000-2023 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 <https://www.openssl.org/source/license.html>.

3.0.13                                       2026-07-29                            OPENSSL-ENC(1SSL)