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    Command Linux
    Home - man page - OPENSSL

    OPENSSL

    WillieBy WillieApril 21, 2026Updated:April 21, 2026No Comments6 Mins Read
     

    NAME

    openssl – OpenSSL command line tool  

    SYNOPSIS

    openssl command [ command_opts ] [ command_args ]

    openssl [ list-standard-commands | list-message-digest-commands | list-cipher-commands | list-cipher-algorithms | list-message-digest-algorithms | list-public-key-algorithms]

    openssl no-XXX [ arbitrary 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 tool 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
     o  Encryption and Decryption with Ciphers
     o  SSL/TLS Client and Server Tests
     o  Handling of S/MIME signed or encrypted mail
     o  Time Stamp requests, generation and verification
    
    
     

    COMMAND SUMMARY

    The openssl program provides a rich variety of commands (command in the SYNOPSIS above), each of which often has a wealth of options and arguments (command_opts and command_args in the SYNOPSIS).

    The pseudo-commands list-standard-commands, list-message-digest-commands, and list-cipher-commands output a list (one entry per line) of the names of all standard commands, message digest commands, or cipher commands, respectively, that are available in the present openssl utility.

    The pseudo-commands list-cipher-algorithms and list-message-digest-algorithms list all cipher and message digest names, one entry per line. Aliases are listed as:

     from => to
    
    

    The pseudo-command list-public-key-algorithms lists all supported public key algorithms.

    The pseudo-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-…-commands, or no-XXX itself.)  

    STANDARD COMMANDS

    asn1parse
    Parse an ASN.1 sequence.
    ca
    Certificate Authority (CA) Management.
    ciphers
    Cipher Suite Description Determination.
    cms
    CMS (Cryptographic Message Syntax) utility
    crl
    Certificate Revocation List (CRL) Management.
    crl2pkcs7
    CRL to PKCS#7 Conversion.
    dgst
    Message Digest Calculation.
    dh
    Diffie-Hellman Parameter Management. Obsoleted by dhparam.
    dhparam
    Generation and Management of Diffie-Hellman Parameters. Superseded by genpkey and pkeyparam
    dsa
    DSA Data Management.
    dsaparam
    DSA Parameter Generation and Management. Superseded by genpkey and pkeyparam
    ec
    EC (Elliptic curve) key processing
    ecparam
    EC parameter manipulation and generation
    enc
    Encoding with Ciphers.
    engine
    Engine (loadble module) information and manipulation.
    errstr
    Error Number to Error String Conversion.
    gendh
    Generation of Diffie-Hellman Parameters. Obsoleted by dhparam.
    gendsa
    Generation of DSA Private Key from Parameters. Superseded by genpkey and pkey
    genpkey
    Generation of Private Key or Parameters.
    genrsa
    Generation of RSA Private Key. Superceded by genpkey.
    nseq
    Create or examine a netscape certificate sequence
    ocsp
    Online Certificate Status Protocol utility.
    passwd
    Generation of hashed passwords.
    pkcs12
    PKCS#12 Data Management.
    pkcs7
    PKCS#7 Data Management.
    pkey
    Public and private key management.
    pkeyparam
    Public key algorithm parameter management.
    pkeyutl
    Public key algorithm cryptographic operation utility.
    rand
    Generate pseudo-random bytes.
    req
    PKCS#10 X.509 Certificate Signing Request (CSR) Management.
    rsa
    RSA key management.
    rsautl
    RSA utility for signing, verification, encryption, and decryption. Superseded by pkeyutl
    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 utility
    ts
    Time Stamping Authority tool (client/server)
    verify
    X.509 Certificate Verification.
    version
    OpenSSL Version Information.
    x509
    X.509 Certificate Data Management.
     

    MESSAGE DIGEST COMMANDS

    md2
    MD2 Digest
    md5
    MD5 Digest
    mdc2
    MDC2 Digest
    rmd160
    RMD-160 Digest
    sha
    SHA Digest
    sha1
    SHA-1 Digest
    sha224
    SHA-224 Digest
    sha256
    SHA-256 Digest
    sha384
    SHA-384 Digest
    sha512
    SHA-512 Digest
     

    ENCODING AND CIPHER COMMANDS

    base64
    Base64 Encoding
    bf bf-cbc bf-cfb bf-ecb bf-ofb
    Blowfish Cipher
    cast cast-cbc
    CAST Cipher
    cast5-cbc cast5-cfb cast5-ecb cast5-ofb
    CAST5 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
     

    PASS PHRASE ARGUMENTS

    Several commands accept password arguments, typically using -passin and -passout for input and output passwords respectively. These allow the password to be obtained from a variety of sources. Both of these options take a single argument whose format is described below. If no password argument is given and a password is required then the user is prompted to enter one: this will typically be read from the current terminal with echoing turned off.
    pass:password
    the actual password is password. Since the password is visible to utilities (like ‘ps’ under Unix) this form should only be used where security is not important.
    env:var
    obtain the password from the environment variable var. Since the environment of other processes is visible on certain platforms (e.g. ps under certain Unix OSes) this option should be used with caution.
    file:pathname
    the first line of pathname is the password. If the same pathname argument is supplied to -passin and -passout arguments then the first line will be used for the input password and the next line for the output password. pathname need not refer to a regular file: it could for example refer to a device or named pipe.
    fd:number
    read the password from the file descriptor number. This can be used to send the data via a pipe for example.
    stdin
    read the password from standard input.

    Willie
    • Website

    Willie has over 15 years of experience in Linux system administration and DevOps. After managing infrastructure for startups and enterprises alike, he founded Command Linux to share the practical knowledge he wished he had when starting out. He oversees content strategy and contributes guides on server management, automation, and security.

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