OPENSSL(1SSL)

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version 4.0.3 · 14 versions
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👑 openssl — the OpenSSL command line program 💅

okay bestie, welcome to OPENSSL(1SSL), the manual page for the one and only openssl command line program. this is the main character of the cryptography world, no cap. grab a snack, we're going on a tour ✨

🌸 NAME 🌸

openssl — OpenSSL command line program 🫶

✨ SYNOPSIS ✨

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

openssl no-XXX [ options ]

openssl -help | -version

💖 DESCRIPTION 💖

So. 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. it's giving legendary, it's giving foundational, it's giving everything runs on this. 💀

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

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

like… that's a whole resume. she does it all. 🌈

🎀 COMMAND SUMMARY 🎀

The openssl program provides a rich variety of commands (that's the command in the "SYNOPSIS" up there 👆). 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. iykyk 💅

The command no-XXX tests whether a command of the specified name is available. Here's the vibe: 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. (and heads up — no-XXX is not able to detect pseudo-commands such as quit, list, or no-XXX itself. she has limits okay 😭)

⚙️ 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.
  • ech — Encrypted Client Hello (ECH) admin. See openssl-ech(1).
  • ecparam — EC parameter manipulation and generation.
  • enc — Encryption, decryption, and encoding.
  • 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. not all of them made it to the party, bestie 😭
  • 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 ✨

okay so which options you actually get depends on which specific command you're running 💅 every command does its own thing. but this section is all about the common options that lots of commands share, and their common behaviour.

🎀 Program Options

these ones you can throw at openssl all by themselves, no command needed, just to get help or version tea.

  • -help — drops a terse lil summary of all the options. want the detailed version? every single command supports its own -help option too. and yes, --help works exactly the same 💖
  • -version — terse summary of the openssl program version. for the full lore go read openssl-version(1). also accepts --version.

🫶 Common Options

  • -help — and bestie, if an option takes an argument, this also tells you the "type" of argument it wants.
  • -- — this ends the whole option list, periodt. it's mostly useful when a filename parameter starts with a minus sign (and the program would otherwise get confused 😭), like:
openssl verify [flags...] -- -cert1.pem...

🌸 Format Options

go see the openssl-format-options(1) manual page, she has the details.

🍓 Pass Phrase Options

go see the openssl-passphrase-options(1) manual page 🎀

🌈 Random State Options

okay history lesson: before OpenSSL 1.1.1, it was super common for applications to store info about the state of the random-number generator in a file, load it up at startup, and rewrite it on exit. on modern operating systems that's generally not necessary anymore, because OpenSSL seeds itself from a trusted entropy source provided by the OS 🦋 but these flags are still supported for special platforms or circumstances that might genuinely need them.

lowkey important: it's generally an error to use the same seed file more than once, and every single use of -rand should be paired with -writerand. like, paired. together. 💀
  • -rand files — a file or files full of random data used to seed the random number generator. multiple files can be given, separated by an OS-dependent character: the separator is ; for MS-Windows, , for OpenVMS, and : for all others. another way to hand over multiple files is to just repeat this flag with different filenames. iconic.
  • -writerand file — writes the seed data out to the specified file upon exit. that file can then be used in a subsequent command invocation. the way that it just... carries the vibes forward 👑

👑 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, while servers pick the highest version the client offers that is also supported by the server. very diplomatic, we love to see it ✨

the options below can limit which protocol versions get used, and whether TCP (SSL and TLS) or UDP (DTLS) is used. heads up though: not all protocols and flags may be available, depending on how OpenSSL was built 🫠

  • -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, no cap. only one specific protocol can be given and it cannot be combined with any of the no_ options. also, the no_* options do not work with the s_time and ciphers commands, but they do work with the s_client and s_server commands.
  • -dtls, -dtls1, -dtls1_2 — these specify using DTLS instead of TLS. with -dtls, clients will negotiate any supported DTLS protocol version. use -dtls1 or -dtls1_2 to support only DTLS1.0 or DTLS1.2, respectively.

🧚 Provider Options

  • -provider name — load and initialize the provider identified by name. the name can also be a path to the provider module, and in that case the provider name will be that specified path and not just the provider module name. how relative paths get interpreted is platform specific 🙈 the configured "MODULESDIR" path, the OPENSSL_MODULES environment variable, or the path specified by -provider-path gets prepended to relative paths. see provider(7) for the whole detailed description.
  • -provider-path path — specifies the search path to be used when looking for providers. equivalently, you can set the OPENSSL_MODULES environment variable instead.
  • -provparam [name:]key=value — set configuration parameter key to val in provider name (that part's optional). if name isn't specified, the setting gets applied to all loaded providers. this option can be specified multiple times to set multiple parameters. options that specify nondefault providers to load should come before this option if the setting is intended to apply to those 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 effect when set through this interface. only UTF8-string-valued parameters are supported. for any supported parameters, go read the documentation of the specific provider and associated algorithms 💅
  • -propquery propq — specifies the property query clause to be used when fetching algorithms from the loaded providers. see property(7) for the more detailed description.

🌍 ENVIRONMENT 🌍

the OpenSSL libraries can take some configuration parameters straight from the environment 💫

for info about all the environment variables used by the OpenSSL libraries — things like OPENSSL_CONF, OPENSSL_MODULES, and OPENSSL_TRACE — go see openssl-env(7).

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

for info about specific commands, see openssl-rehash(1) and tsget(1).

for info about querying or specifying CPU architecture flags, see OPENSSL_armcap(3), OPENSSL_ia32cap(3), OPENSSL_ppccap(3), OPENSSL_s390xcap(3) and OPENSSL_riscvcap(3).

🔍 SEE ALSO 🔍

so much family. okay, deep breath: 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-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 💀 like it just pretends you didn't say it.
  • 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 — running that program with no arguments is now equivalent to openssl help.
  • the engine command, the whole engine support together with the org.openssl.engine URI scheme was removed in OpenSSL 4.0; use providers as a replacement.

Copyright 2000-2026 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.

and that's the whole page bestie 🫶 this one's from version 4.0.3, dated 2026-09-29 — go forth and openssl responsibly, mwah 💅✨

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