OpenSSL command line tool.

      openssl command [ command_opts ] [ command_args ]

      openssl [ list-standard-commands | list-message-digest-commands | list-cipher-commands ]

      openssl no-XXX [ arbitrary options ]

       asn1parse Parse an ASN.1 sequence.

       ca        Certificate Authority (CA) Management.

       ciphers   Cipher Suite Description Determination.

       crl       Certificate Revocation List (CRL) Management.

       crl2pkcs7 CRL to PKCS#7 Conversion.

       dgst      Message Digest Calculation.

       dh        Diffie-Hellman Parameter Management.  Obsoleted by dhparam.

       dsa       DSA Data Management.

       dsaparam  DSA Parameter Generation.

       enc       Encoding with Ciphers.

       errstr    Error Number to Error String Conversion.

       dhparam   Generation and Management of Diffie-Hellman Parameters.

       gendh     Generation of Diffie-Hellman Parameters.  Obsoleted by dhparam.

       gendsa    Generation of DSA Parameters.

       genrsa    Generation of RSA Parameters.

       ocsp      Online Certificate Status Protocol utility.

       passwd    Generation of hashed passwords.

       pkcs12    PKCS#12 Data Management.

       pkcs7     PKCS#7 Data Management.

       rand [options] num   Generate pseudo-random bytes.
                 When converted to base64, an additional pad character "0" may be suffixed to
                 make the encoded output an integer multiple of 4 characters.
                 If the unencoded binary text is a multiple of 3 bytes (3,6,9,12,15,18...)
                 then no pad characters will be added to the output.
                 3 bytes> 4 characters, 6 bytes>8 characters etc.

       req       X.509 Certificate Signing Request (CSR) Management.

       rsa       RSA Data Management.

       rsautl    RSA utility for signing, verification, encryption, and decryption.

       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.

       verify    X.509 Certificate Verification.

       version   OpenSSL Version Information.

       x509      X.509 Certificate Data Management.

       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

       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
       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.

                 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

       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.

                 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.

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


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-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.)


Generate a random 20 character password, 15 random bytes (8 bits each) will be converted to 20 characters in base 64 (6 bits of entropy per character):

openssl rand -base64 15

Verify a manually-downloaded software update (InstallESD.dmg) from Apple Downloads, which contains a SHA-1 digest

$ openssl sha1 /Volumes/Install\ macOS\ Sierra\ 12.5.03/Install\ macOS\
SHA1(/Volumes/Install macOS Sierra 12.5.03/Install macOS 51df126965433187403987c9d74d95c26cba9266

This can be compared with a list of known good file hashes. e.g. OSX SHA1 Checksums

“Programming is dreadfully impermanent; it’s more like performance art than literature” ~ Bruce Sterling

Related macOS commands

asn1parse(1), ca(1), config(5), crl(1), crl2pkcs7(1), dgst(1), dhparam(1), dsa(1), dsaparam(1), enc(1), gendsa(1), genrsa(1), nseq(1)
passwd - Modify a user password.
pbcopy - Copy data to the clipboard.
pkcs12(1), pkcs7(1), pkcs8(1), rand(1), req(1), rsa(1), rsautl(1), s_client(1), s_server(1), s_time(1), smime(1), spkac(1), verify(1), version(1), x509(1), crypto(3), ssl(3)

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