Cryptography and SSL/TLS Toolkit



openssl - OpenSSL command line program


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

openssl no-XXX [ options ]

openssl -help | -version


OpenSSL is a cryptography toolkit implementing the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) 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


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


Parse an ASN.1 sequence.


Certificate Authority (CA) Management.


Cipher Suite Description Determination.


CMS (Cryptographic Message Syntax) command.


Certificate Revocation List (CRL) Management.


CRL to PKCS#7 Conversion.


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 MAC calculations are superseded by openssl-mac(1).


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 Superseded by openssl-genpkey(1) and openssl-pkeyparam(1).


DSA Data Management.


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 Superseded by openssl-genpkey(1) and openssl-pkeyparam(1).


EC (Elliptic curve) key processing.


EC parameter manipulation and generation.


Encryption, decryption, and encoding.


Engine (loadable module) information and manipulation.


Error Number to Error String Conversion.


FIPS configuration installation.


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 Superseded by openssl-genpkey(1) and openssl-pkey(1).


Generation of Private Key or Parameters.


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 Superseded by openssl-genpkey(1).


Display information about a command's options.


Display diverse information built into the OpenSSL libraries.


Key Derivation Functions.


List algorithms and features.


Message Authentication Code Calculation.


Create or examine a Netscape certificate sequence.


Online Certificate Status Protocol command.


Generation of hashed passwords.


PKCS#12 Data Management.


PKCS#7 Data Management.


PKCS#8 format private key conversion command.


Public and private key management.


Public key algorithm parameter management.


Public key algorithm cryptographic operation command.


Compute prime numbers.


Generate pseudo-random bytes.


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


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


RSA key management.


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 Superseded by openssl-pkeyutl(1).


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.


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.


SSL Connection Timer.


SSL Session Data Management.


S/MIME mail processing.


Algorithm Speed Measurement.


SPKAC printing and generating command.


Maintain SRP password file. This command is deprecated.


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


Time Stamping Authority command.


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


OpenSSL Version Information.


X.509 Certificate Data Management.

Message Digest Commands


BLAKE2b-512 Digest


BLAKE2s-256 Digest


MD2 Digest


MD4 Digest


MD5 Digest


MDC2 Digest


RMD-160 Digest


SHA-1 Digest


SHA-2 224 Digest


SHA-2 256 Digest


SHA-2 384 Digest


SHA-2 512 Digest


SHA-3 224 Digest


SHA-3 256 Digest


SHA-3 384 Digest


SHA-3 512 Digest


KECCAK 224 Digest


KECCAK 256 Digest


KECCAK 384 Digest


KECCAK 512 Digest


SHA-3 SHAKE128 Digest


SHA-3 SHAKE256 Digest


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 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 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 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


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

Program Options

These options can be specified without a command specified to get help or version information.


Provides a terse summary of all options. For more detailed information, each command supports a -help option. Accepts --help as well.


Provides a terse summary of the openssl program version. For more detailed information see openssl-version(1). Accepts --version as well.

Common 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:


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.


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), OPENSSL_s390xcap(3) and OPENSSL_riscvcap(3).

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


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 if OpenSSL was built without tracing support.

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


Traces the OpenSSL trace API itself.


Traces OpenSSL library initialization and cleanup.


Traces the TLS/SSL protocol.


Traces the ciphers used by the TLS/SSL protocol.


Show details about provider and engine configuration.


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


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


Traces PKCS#5 v2 key generation.


Traces PKCS#12 key generation.


Traces PKCS#12 decryption.


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


Traces BIGNUM context operations.


Traces CMP client and server activity.


Traces STORE operations.


Traces decoder operations.


Traces encoder operations.


Traces decrementing certain ASN.1 structure references.


Traces the HTTP client and server, such as messages being sent and received.


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)


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 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