Using OpenSSL to calculate Message Digest

The md5sum command can be used to calculate an MD5 message digest (MD5 is an abbreviation for "Message-Digest algorithm 5"), which is a cryptographic hash function. The md5sum program is commonly found on Linux systems and programs which the provide the same functionality are also available for Microsoft Windows systems, e.g. digestIT 2004. But, if such a program isn't present on a system, e.g. an OS X system, but OpenSSL is present, you can use the openssl command to obtain message digests, which can allow you to verify that a file, such as an executable file, was not changed since it was released by the originator.

If you issue the command openssl dgst filename, openssl will, by default, provide the MD5 checksum for the file. You can also use other cryptographic hash functions, such as SHA, SHA1, MD2, or you can specify MD5.

$ openssl dgst images.zip
MD5(images.zip)= 796faa884fb0125eda60cd5e8aa8daa1
$ openssl md5 images.zip
MD5(images.zip)= 796faa884fb0125eda60cd5e8aa8daa1
$ openssl sha1 images.zip
SHA1(images.zip)= 3070ac89b7a4327e217045b1cac790c1dc048d8f
$ openssl sha images.zip
SHA(images.zip)= 021e35f63c55e22355bea99f73df885659a46d15
$ openssl md2 images.zip
MD2(images.zip)= 47bd3f0cc33710997f2fe57b1f7cc2c5

The available message digest options include the following:

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

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