man > openssl(1)

TLDR: openssl (tldr-pages)

OpenSSL cryptographic toolkit.

  • Generate a private key and encrypt the output file using AES-256
    openssl genpkey -algorithm {{rsa|ec}} -out {{path/to/private.key}} -aes256
  • Generate the corresponding public key from the private key `private.key` using `rsa`
    openssl rsa -in {{path/to/private.key}} -pubout -out {{path/to/public.key}}
  • Generate a self-signed certificate valid for a specified number of days (365)
    openssl req -new -x509 -key {{path/to/private.key}} -out {{path/to/certificate.crt}} -days 365
  • Convert a certificate to `.pem` or `.der` format
    openssl x509 -in {{path/to/certificate.crt}} -out {{path/to/certificate.pem|path/to/certificate.der}} -outform {{pem|der}}
  • Check certificate details
    openssl x509 -in {{path/to/certificate.crt}} -text -noout
  • Generate a certificate signing request (CSR)
    openssl req -new -key {{path/to/private.key}} -out {{path/to/request.csr}}
  • Display help
    openssl help
  • Display version
    openssl version
OPENSSL(1SSL)                                  OpenSSL                                 OPENSSL(1SSL)

NAME
       openssl - OpenSSL command line program

SYNOPSIS
       openssl command [ options ... ] [ parameters ... ]

       openssl no-XXX [ options ]

DESCRIPTION
       OpenSSL is a cryptography toolkit implementing the Secure Sockets Layer (SSL v2/v3) and
       Transport Layer Security (TLS v1) network protocols and related cryptography standards
       required by them.

       The openssl program is a command line program for using the various cryptography functions of
       OpenSSL's crypto library from the shell.  It can be used for

        o  Creation and management of private keys, public keys and parameters
        o  Public key cryptographic operations
        o  Creation of X.509 certificates, CSRs and CRLs
        o  Calculation of Message Digests and Message Authentication Codes
        o  Encryption and Decryption with Ciphers
        o  SSL/TLS Client and Server Tests
        o  Handling of S/MIME signed or encrypted mail
        o  Timestamp requests, generation and verification

COMMAND SUMMARY
       The openssl program provides a rich variety of commands (command in the "SYNOPSIS" above).
       Each command can have many options and argument parameters, shown above as options and
       parameters.

       Detailed documentation and use cases for most standard subcommands are available (e.g.,
       openssl-x509(1)). The subcommand openssl-list(1) may be used to list subcommands.

       The command no-XXX tests whether a command of the specified name is available.  If no command
       named XXX exists, it returns 0 (success) and prints no-XXX; otherwise it returns 1 and prints
       XXX.  In both cases, the output goes to stdout and nothing is printed to stderr.  Additional
       command line arguments are always ignored.  Since for each cipher there is a command of the
       same name, this provides an easy way for shell scripts to test for the availability of
       ciphers in the openssl program.  (no-XXX is not able to detect pseudo-commands such as quit,
       list, or no-XXX itself.)

   Configuration Option
       Many commands use an external configuration file for some or all of their arguments and have
       a -config option to specify that file.  The default name of the file is openssl.cnf in the
       default certificate storage area, which can be determined from the openssl-version(1) command
       using the -d or -a option.  The environment variable OPENSSL_CONF can be used to specify a
       different file location or to disable loading a configuration (using the empty string).

       Among others, the configuration file can be used to load modules and to specify parameters
       for generating certificates and random numbers.  See config(5) for details.

   Standard Commands
       asn1parse
           Parse an ASN.1 sequence.

       ca  Certificate Authority (CA) Management.

       ciphers
           Cipher Suite Description Determination.

       cms CMS (Cryptographic Message Syntax) command.

       crl Certificate Revocation List (CRL) Management.

       crl2pkcs7
           CRL to PKCS#7 Conversion.

       dgst
           Message Digest calculation. MAC calculations are superseded by openssl-mac(1).

       dhparam
           Generation  and Management of Diffie-Hellman Parameters. Superseded by openssl-genpkey(1)
           and openssl-pkeyparam(1).

       dsa DSA Data Management.

       dsaparam
           DSA  Parameter  Generation  and  Management.   Superseded   by   openssl-genpkey(1)   and
           openssl-pkeyparam(1).

       ec  EC (Elliptic curve) key processing.

       ecparam
           EC parameter manipulation and generation.

       enc Encryption, decryption, and encoding.

       engine
           Engine (loadable module) information and manipulation.

       errstr
           Error Number to Error String Conversion.

       fipsinstall
           FIPS configuration installation.

       gendsa
           Generation  of  DSA  Private  Key  from  Parameters. Superseded by openssl-genpkey(1) and
           openssl-pkey(1).

       genpkey
           Generation of Private Key or Parameters.

       genrsa
           Generation of RSA Private Key. Superseded by openssl-genpkey(1).

       help
           Display information about a command's options.

       info
           Display diverse information built into the OpenSSL libraries.

       kdf Key Derivation Functions.

       list
           List algorithms and features.

       mac Message Authentication Code Calculation.

       nseq
           Create or examine a Netscape certificate sequence.

       ocsp
           Online Certificate Status Protocol command.

       passwd
           Generation of hashed passwords.

       pkcs12
           PKCS#12 Data Management.

       pkcs7
           PKCS#7 Data Management.

       pkcs8
           PKCS#8 format private key conversion command.

       pkey
           Public and private key management.

       pkeyparam
           Public key algorithm parameter management.

       pkeyutl
           Public key algorithm cryptographic operation command.

       prime
           Compute prime numbers.

       rand
           Generate pseudo-random bytes.

       rehash
           Create symbolic links to certificate and CRL files named by the hash values.

       req PKCS#10 X.509 Certificate Signing Request (CSR) Management.

       rsa RSA key management.

       rsautl
           RSA  command  for  signing,  verification,  encryption,  and  decryption.  Superseded  by
           openssl-pkeyutl(1).

       s_client
           This  implements a generic SSL/TLS client which can establish a transparent connection to
           a remote server speaking SSL/TLS. It's intended for testing purposes  only  and  provides
           only  rudimentary interface functionality but internally uses mostly all functionality of
           the OpenSSL ssl library.

       s_server
           This implements a generic SSL/TLS server which accepts connections  from  remote  clients
           speaking  SSL/TLS.  It's intended for testing purposes only and provides only rudimentary
           interface functionality but internally uses mostly all functionality of the  OpenSSL  ssl
           library.   It  provides  both  an  own  command  line  oriented  protocol for testing SSL
           functions and a simple HTTP response facility to emulate an SSL/TLS-aware webserver.

       s_time
           SSL Connection Timer.

       sess_id
           SSL Session Data Management.

       smime
           S/MIME mail processing.

       speed
           Algorithm Speed Measurement.

       spkac
           SPKAC printing and generating command.

       srp Maintain SRP password file. This command is deprecated.

       storeutl
           Command to list and display certificates, keys, CRLs, etc.

       ts  Time Stamping Authority command.

       verify
           X.509 Certificate Verification.   See  also  the  openssl-verification-options(1)  manual
           page.

       version
           OpenSSL Version Information.

       x509
           X.509 Certificate Data Management.

   Message Digest Commands
       blake2b512
           BLAKE2b-512 Digest

       blake2s256
           BLAKE2s-256 Digest

       md2 MD2 Digest

       md4 MD4 Digest

       md5 MD5 Digest

       mdc2
           MDC2 Digest

       rmd160
           RMD-160 Digest

       sha1
           SHA-1 Digest

       sha224
           SHA-2 224 Digest

       sha256
           SHA-2 256 Digest

       sha384
           SHA-2 384 Digest

       sha512
           SHA-2 512 Digest

       sha3-224
           SHA-3 224 Digest

       sha3-256
           SHA-3 256 Digest

       sha3-384
           SHA-3 384 Digest

       sha3-512
           SHA-3 512 Digest

       shake128
           SHA-3 SHAKE128 Digest

       shake256
           SHA-3 SHAKE256 Digest

       sm3 SM3 Digest

   Encryption, Decryption, and Encoding Commands
       The following aliases provide convenient access to the most used encodings and ciphers.

       Depending  on  how  OpenSSL  was  configured  and  built,  not all ciphers listed here may be
       present. See openssl-enc(1) for more information.

       aes128, aes-128-cbc, aes-128-cfb, aes-128-ctr, aes-128-ecb, aes-128-ofb
           AES-128 Cipher

       aes192, aes-192-cbc, aes-192-cfb, aes-192-ctr, aes-192-ecb, aes-192-ofb
           AES-192 Cipher

       aes256, aes-256-cbc, aes-256-cfb, aes-256-ctr, aes-256-ecb, aes-256-ofb
           AES-256 Cipher

       aria128, aria-128-cbc, aria-128-cfb, aria-128-ctr, aria-128-ecb, aria-128-ofb
           Aria-128 Cipher

       aria192, aria-192-cbc, aria-192-cfb, aria-192-ctr, aria-192-ecb, aria-192-ofb
           Aria-192 Cipher

       aria256, aria-256-cbc, aria-256-cfb, aria-256-ctr, aria-256-ecb, aria-256-ofb
           Aria-256 Cipher

       base64
           Base64 Encoding

       bf, bf-cbc, bf-cfb, bf-ecb, bf-ofb
           Blowfish Cipher

       camellia128, camellia-128-cbc, camellia-128-cfb, camellia-128-ctr, camellia-128-ecb,
       camellia-128-ofb
           Camellia-128 Cipher

       camellia192, camellia-192-cbc, camellia-192-cfb, camellia-192-ctr, camellia-192-ecb,
       camellia-192-ofb
           Camellia-192 Cipher

       camellia256, camellia-256-cbc, camellia-256-cfb, camellia-256-ctr, camellia-256-ecb,
       camellia-256-ofb
           Camellia-256 Cipher

       cast, cast-cbc
           CAST Cipher

       cast5-cbc, cast5-cfb, cast5-ecb, cast5-ofb
           CAST5 Cipher

       chacha20
           Chacha20 Cipher

       des, des-cbc, des-cfb, des-ecb, des-ede, des-ede-cbc, des-ede-cfb, des-ede-ofb, des-ofb
           DES Cipher

       des3, desx, des-ede3, des-ede3-cbc, des-ede3-cfb, des-ede3-ofb
           Triple-DES Cipher

       idea, idea-cbc, idea-cfb, idea-ecb, idea-ofb
           IDEA Cipher

       rc2, rc2-cbc, rc2-cfb, rc2-ecb, rc2-ofb
           RC2 Cipher

       rc4 RC4 Cipher

       rc5, rc5-cbc, rc5-cfb, rc5-ecb, rc5-ofb
           RC5 Cipher

       seed, seed-cbc, seed-cfb, seed-ecb, seed-ofb
           SEED Cipher

       sm4, sm4-cbc, sm4-cfb, sm4-ctr, sm4-ecb, sm4-ofb
           SM4 Cipher

OPTIONS
       Details of which options  are  available  depend  on  the  specific  command.   This  section
       describes some common options with common behavior.

   Common Options
       -help
           Provides  a  terse summary of all options.  If an option takes an argument, the "type" of
           argument is also given.

       --  This terminates the list of options. It is mostly useful if any filename parameters start
           with a minus sign:

            openssl verify [flags...] -- -cert1.pem...

   Format Options
       See openssl-format-options(1) for manual page.

   Pass Phrase Options
       See the openssl-passphrase-options(1) manual page.

   Random State Options
       Prior to OpenSSL 1.1.1, it was common for applications to store information about  the  state
       of  the random-number generator in a file that was loaded at startup and rewritten upon exit.
       On modern operating systems, this is generally no  longer  necessary  as  OpenSSL  will  seed
       itself  from a trusted entropy source provided by the operating system. These flags are still
       supported for special platforms or circumstances that might require them.

       It is generally an error to use the same seed file more than once  and  every  use  of  -rand
       should be paired with -writerand.

       -rand files
           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
           ";" for MS-Windows, "," for OpenVMS, and ":" for  all  others.  Another  way  to  specify
           multiple files is to repeat this flag with different filenames.

       -writerand file
           Writes  the  seed  data  to  the  specified  file  upon exit.  This file can be used in a
           subsequent command invocation.

   Certificate Verification Options
       See the openssl-verification-options(1) manual page.

   Name Format Options
       See the openssl-namedisplay-options(1) manual page.

   TLS Version Options
       Several commands use SSL, TLS, or DTLS. By default, the commands use  TLS  and  clients  will
       offer the lowest and highest protocol version they support, and servers will pick the highest
       version that the client offers that is also supported by the server.

       The options below can be used to limit which protocol versions are used, and whether TCP (SSL
       and  TLS)  or  UDP  (DTLS)  is used.  Note that not all protocols and flags may be available,
       depending on how OpenSSL was built.

       -ssl3, -tls1, -tls1_1, -tls1_2, -tls1_3, -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2,
       -no_tls1_3
           These options require or disable the use of the specified SSL or TLS protocols.   When  a
           specific  TLS  version  is required, only that version will be offered or accepted.  Only
           one specific protocol can be given and it cannot be combined with any of the no_ options.
           The no_* options do not work with s_time and ciphers commands but work with s_client  and
           s_server commands.

       -dtls, -dtls1, -dtls1_2
           These options specify to use DTLS instead of TLS.  With -dtls, clients will negotiate any
           supported  DTLS  protocol  version.   Use  the -dtls1 or -dtls1_2 options to support only
           DTLS1.0 or DTLS1.2, respectively.

   Engine Options
       -engine id
           Load the engine identified by id and use all the methods it implements  (algorithms,  key
           storage, etc.), unless specified otherwise in the command-specific documentation or it is
           configured to do so, as described in "Engine Configuration" in config(5).

           The  engine  will  be  used  for  key ids specified with -key and similar options when an
           option like -keyform engine is given.

           A special case is the "loader_attic" engine, which is meant  just  for  internal  OpenSSL
           testing  purposes  and  supports  loading  keys,  parameters, certificates, and CRLs from
           files.  When this engine is used, files with such credentials are read via  this  engine.
           Using the "file:" schema is optional; a plain file (path) name will do.

       Options  specifying  keys,  like  -key  and  similar,  can use the generic OpenSSL engine key
       loading URI scheme "org.openssl.engine:" to retrieve private keys and public keys.   The  URI
       syntax is as follows, in simplified form:

           org.openssl.engine:{engineid}:{keyid}

       Where  "{engineid}"  is  the  identity/name  of the engine, and "{keyid}" is a key identifier
       that's acceptable by that engine.  For example, when using an engine that interfaces  against
       a  PKCS#11  implementation, the generic key URI would be something like this (this happens to
       be an example for the PKCS#11 engine that's part of OpenSC):

           -key org.openssl.engine:pkcs11:label_some-private-key

       As  a  third  possibility,  for  engines  and  providers  that  have  implemented  their  own
       OSSL_STORE_LOADER(3),   "org.openssl.engine:"   should  not  be  necessary.   For  a  PKCS#11
       implementation that has implemented such a loader, the PKCS#11 URI as  defined  in  RFC  7512
       should be possible to use directly:

           -key pkcs11:object=some-private-key;pin-value=1234

   Provider Options
       -provider name
           Load  and  initialize the provider identified by name. The name can be also a path to the
           provider module. In that case the provider name will be the specified path and  not  just
           the  provider  module  name.   Interpretation of relative paths is platform specific. The
           configured "MODULESDIR" path, OPENSSL_MODULES environment variable, or the path specified
           by -provider-path is prepended to relative paths.  See provider(7) for  a  more  detailed
           description.

       -provider-path path
           Specifies  the  search  path that is to be used for looking for providers.  Equivalently,
           the OPENSSL_MODULES environment variable may be set.

       -propquery propq
           Specifies the property query clause to be used when fetching algorithms from  the  loaded
           providers.  See property(7) for a more detailed description.

ENVIRONMENT
       The  OpenSSL library can be take some configuration parameters from the environment.  Some of
       these  variables  are  listed  below.   For  information   about   specific   commands,   see
       openssl-engine(1), openssl-rehash(1), and tsget(1).

       For information about the use of environment variables in configuration, see "ENVIRONMENT" in
       config(5).

       For  information about querying or specifying CPU architecture flags, see OPENSSL_ia32cap(3),
       and OPENSSL_s390xcap(3).

       For  information  about  all  environment  variables  used  by  the  OpenSSL  libraries,  see
       openssl-env(7).

       OPENSSL_TRACE=name[,...]
           Enable  tracing  output of OpenSSL library, by name.  This output will only make sense if
           you know OpenSSL internals well.  Also,  it  might  not  give  you  any  output  at  all,
           depending on how OpenSSL was built.

           The value is a comma separated list of names, with the following available:

           TRACE
               Traces the OpenSSL trace API itself.

           INIT
               Traces OpenSSL library initialization and cleanup.

           TLS Traces the TLS/SSL protocol.

           TLS_CIPHER
               Traces the ciphers used by the TLS/SSL protocol.

           CONF
               Show details about provider and engine configuration.

           ENGINE_TABLE
               The  function that is used by RSA, DSA (etc) code to select registered ENGINEs, cache
               defaults and functional references (etc), will generate debugging summaries.

           ENGINE_REF_COUNT
               Reference counts in the ENGINE structure will be monitored with a line  of  generated
               for each change.

           PKCS5V2
               Traces PKCS#5 v2 key generation.

           PKCS12_KEYGEN
               Traces PKCS#12 key generation.

           PKCS12_DECRYPT
               Traces PKCS#12 decryption.

           X509V3_POLICY
               Generates  the  complete  policy  tree  at  various  points  during  X.509  v3 policy
               evaluation.

           BN_CTX
               Traces BIGNUM context operations.

           CMP Traces CMP client and server activity.

           STORE
               Traces STORE operations.

           DECODER
               Traces decoder operations.

           ENCODER
               Traces encoder operations.

           REF_COUNT
               Traces decrementing certain ASN.1 structure references.

SEE ALSO
       openssl-asn1parse(1),  openssl-ca(1),  openssl-ciphers(1),  openssl-cms(1),   openssl-crl(1),
       openssl-crl2pkcs7(1),        openssl-dgst(1),       openssl-dhparam(1),       openssl-dsa(1),
       openssl-dsaparam(1), openssl-ec(1),  openssl-ecparam(1),  openssl-enc(1),  openssl-engine(1),
       openssl-errstr(1),  openssl-gendsa(1), openssl-genpkey(1), openssl-genrsa(1), openssl-kdf(1),
       openssl-list(1),   openssl-mac(1),   openssl-nseq(1),   openssl-ocsp(1),   openssl-passwd(1),
       openssl-pkcs12(1), openssl-pkcs7(1), openssl-pkcs8(1), openssl-pkey(1), openssl-pkeyparam(1),
       openssl-pkeyutl(1),  openssl-prime(1),  openssl-rand(1),  openssl-rehash(1),  openssl-req(1),
       openssl-rsa(1),      openssl-rsautl(1),       openssl-s_client(1),       openssl-s_server(1),
       openssl-s_time(1),  openssl-sess_id(1), openssl-smime(1), openssl-speed(1), openssl-spkac(1),
       openssl-srp(1), openssl-storeutl(1),  openssl-ts(1),  openssl-verify(1),  openssl-version(1),
       openssl-x509(1), config(5), crypto(7), openssl-env(7).  ssl(7), x509v3_config(5)

HISTORY
       The  list  -XXX-algorithms options were added in OpenSSL 1.0.0; For notes on the availability
       of other commands, see their individual manual pages.

       The -issuer_checks option is deprecated as of OpenSSL 1.1.0 and is silently ignored.

       The -xcertform and -xkeyform options are obsolete since OpenSSL 3.0 and have no effect.

       The interactive mode, which could be invoked by running "openssl" with no further  arguments,
       was  removed  in OpenSSL 3.0, and running that program with no arguments is now equivalent to
       "openssl help".

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(1SSL)
openssl(1)
NAME SYNOPSIS DESCRIPTION COMMAND SUMMARY
Configuration Option Standard Commands asn1parse ciphers crl2pkcs7 dgst dhparam dsaparam ecparam engine errstr fipsinstall gendsa genpkey genrsa help info list nseq ocsp passwd pkcs12 pkcs7 pkcs8 pkey pkeyparam pkeyutl prime rand rehash rsautl s_client s_server s_time sess_id smime speed spkac storeutl verify version x509 Message Digest Commands blake2b512 blake2s256 mdc2 rmd160 sha1 sha224 sha256 sha384 sha512 sha3-224 sha3-256 sha3-384 sha3-512 shake128 shake256 Encryption, Decryption, and Encoding Commands base64 camellia-128-ofb camellia-192-ofb camellia-256-ofb chacha20
OPTIONS
Common Options -help Format Options Pass Phrase Options Random State Options -rand files -writerand file Certificate Verification Options Name Format Options TLS Version Options -ssl3, -tls1, -tls1_1, -tls1_2, -tls1_3, -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2, -no_tls1_3 -dtls, -dtls1, -dtls1_2 Engine Options -engine id Provider Options -provider name -provider-path path -propquery propq
ENVIRONMENT SEE ALSO HISTORY COPYRIGHT

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