openssl - OpenSSL command line program
SYNOPSIS
openssl command [ options ... ] [ parameters ... ]
openssl no-XXX [ options ]
openssl -help | -version
DESCRIPTION
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
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
keccak-224
KECCAK 224 Digest
keccak-256
KECCAK 256 Digest
keccak-384
KECCAK 384 Digest
keccak-512
KECCAK 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.
Program Options
These options can be specified without a command specified to get help or version information.
-help
Provides a terse summary of all options. For more detailed information, each command supports a -help option. Accepts --help as well.
-version
Provides a terse summary of the openssl program version. For more detailed information see openssl-version(1). Accepts --version as well.
Common Options
-help
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 MSWindows, "," 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.
-provparam [name:]key=value
Set configuration parameter key to value val in provider name (optional), if name is not specified, the setting will be applied to all loaded providers. This option can be specified multiple times, to set multiple parameters. Options that specify nondefault providers to load should precede this option if the setting is intended to apply to the to be loaded providers. Parameters that only affect provider initialisation must, for now, be set in the configuration file, only parameters that are also queried as needed later have any affect when set via this interface. Only UTF8-string-valued parameters are supported. See the documentation of the specific provider and associated algorithms for any supported parameters.
-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 libraries can take some configuration parameters from the environment.
For information about all environment variables used by the OpenSSL libraries, such as OPENSSL_CONF, OPENSSL_MODULES, and OPENSSL_TRACE, see openssl-env(7).
For information about the use of environment variables in configuration, see "ENVIRONMENT" in config(5).
For information about specific commands, see openssl-engine(1), openssl-rehash(1), and tsget(1).
For information about querying or specifying CPU architecture flags, see OPENSSL_ia32cap(3), OPENSSL_s390xcap(3) and OPENSSL_riscvcap(3).
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 2000-2025 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].