dgst, sha, sha1, mdc2, ripemd160, sha224, sha256, sha384, sha512, md2,
   md4, md5, dss1 - message digests


   openssl dgst
   [-c] [-d] [-hex] [-binary] [-r] [-non-fips-allow] [-out filename]
   [-sign filename] [-keyform arg] [-passin arg] [-verify filename]
   [-prverify filename] [-signature filename] [-hmac key]
   [-non-fips-allow] [-fips-fingerprint] [file...]

   openssl [digest] [...]


   The digest functions output the message digest of a supplied file or
   files in hexadecimal.  The digest functions also generate and verify
   digital signatures using message digests.


   -c  print out the digest in two digit groups separated by colons, only
       relevant if hex format output is used.

   -d  print out BIO debugging information.

       digest is to be output as a hex dump. This is the default case for
       a "normal" digest as opposed to a digital signature.  See NOTES
       below for digital signatures using -hex.

       output the digest or signature in binary form.

   -r  output the digest in the "coreutils" format used by programs like

       Allow use of non FIPS digest when in FIPS mode.  This has no effect
       when not in FIPS mode.

   -out filename
       filename to output to, or standard output by default.

   -sign filename
       digitally sign the digest using the private key in "filename".

   -keyform arg
       Specifies the key format to sign digest with. The DER, PEM, P12,
       and ENGINE formats are supported.

   -engine id
       Use engine id for operations (including private key storage).  This
       engine is not used as source for digest algorithms, unless it is
       also specified in the configuration file.

   -sigopt nm:v
       Pass options to the signature algorithm during sign or verify
       operations.  Names and values of these options are algorithm-

   -passin arg
       the private key password source. For more information about the
       format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

   -verify filename
       verify the signature using the the public key in "filename".  The
       output is either "Verification OK" or "Verification Failure".

   -prverify filename
       verify the signature using the  the private key in "filename".

   -signature filename
       the actual signature to verify.

   -hmac key
       create a hashed MAC using "key".

   -mac alg
       create MAC (keyed Message Authentication Code). The most popular
       MAC algorithm is HMAC (hash-based MAC), but there are other MAC
       algorithms which are not based on hash, for instance gost-mac
       algorithm, supported by ccgost engine. MAC keys and other options
       should be set via -macopt parameter.

   -macopt nm:v
       Passes options to MAC algorithm, specified by -mac key.  Following
       options are supported by both by HMAC and gost-mac:

               Specifies MAC key as alphnumeric string (use if key contain
               printable characters only). String length must conform to
               any restrictions of the MAC algorithm for example exactly
               32 chars for gost-mac.

               Specifies MAC key in hexadecimal form (two hex digits per
               byte).  Key length must conform to any restrictions of the
               MAC algorithm for example exactly 32 chars for gost-mac.

   -rand file(s)
       a file or files containing random data used to seed the random
       number generator, or an EGD socket (see RAND_egd(3)).  Multiple
       files can be specified separated by a OS-dependent character.  The
       separator is ; for MS-Windows, , for OpenVMS, and : for all others.

       enable use of non-FIPS algorithms such as MD5 even in FIPS mode.

       compute HMAC using a specific key for certain OpenSSL-FIPS

       file or files to digest. If no files are specified then standard
       input is used.


   To create a hex-encoded message digest of a file:
    openssl dgst -md5 -hex file.txt

   To sign a file using SHA-256 with binary file output:
    openssl dgst -sha256 -sign privatekey.pem -out signature.sign file.txt

   To verify a signature:
    openssl dgst -sha256 -verify publickey.pem \
    -signature signature.sign \


   The digest of choice for all new applications is SHA1. Other digests
   are however still widely used.

   When signing a file, dgst will automatically determine the algorithm
   (RSA, ECC, etc) to use for signing based on the private key's ASN.1
   info.  When verifying signatures, it only handles the RSA, DSA, or
   ECDSA signature itself, not the related data to identify the signer and
   algorithm used in formats such as x.509, CMS, and S/MIME.

   A source of random numbers is required for certain signing algorithms,
   in particular ECDSA and DSA.

   The signing and verify options should only be used if a single file is
   being signed or verified.

   Hex signatures cannot be verified using openssl.  Instead, use "xxd -r"
   or similar program to transform the hex signature into a binary
   signature prior to verification.


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.