# module Digest

This module provides a framework for message digest libraries.

You may want to look at `OpenSSL::Digest` as it supports more algorithms.

A cryptographic hash function is a procedure that takes data and returns a fixed bit string: the hash value, also known as digest. `Hash` functions are also called one-way functions, it is easy to compute a digest from a message, but it is infeasible to generate a message from a digest.

## Examples¶ ↑

    require 'digest'

    # Compute a complete digest
    Digest::SHA256.digest 'message'       #=> "\xABS\n\x13\xE4Y..."

    sha256 = Digest::SHA256.new
    sha256.digest 'message'               #=> "\xABS\n\x13\xE4Y..."

    # Other encoding formats
    Digest::SHA256.hexdigest 'message'    #=> "ab530a13e459..."
    Digest::SHA256.base64digest 'message' #=> "q1MKE+RZFJgr..."

    # Compute digest by chunks
    md5 = Digest::MD5.new
    md5.update 'message1'
    md5 << 'message2'                     # << is an alias for update

    md5.hexdigest                         #=> "94af09c09bb9..."

    # Compute digest for a file
    sha256 = Digest::SHA256.file 'testfile'
    sha256.hexdigest

Additionally digests can be encoded in “bubble babble” format as a sequence of consonants and vowels which is more recognizable and comparable than a hexadecimal digest.

    require 'digest/bubblebabble'

    Digest::SHA256.bubblebabble 'message' #=> "xopoh-fedac-fenyh-..."

See the bubble babble specification at web.mit.edu/kenta/www/one/bubblebabble/spec/jrtrjwzi/draft-huima-01.txt.

## `Digest` algorithms¶ ↑

Different digest algorithms (or hash functions) are available:

`MD5`

  See RFC 1321 The `MD5` Message-Digest Algorithm

RIPEMD-160

  As `Digest::RMD160`. See homes.esat.kuleuven.be/~bosselae/ripemd160.html.

`SHA1`

  See FIPS 180 Secure `Hash` Standard.

SHA2 family

  See FIPS 180 Secure `Hash` Standard which defines the following algorithms:

  - SHA512

  - SHA384

  - SHA256

The latest versions of the FIPS publications can be found here: csrc.nist.gov/publications/PubsFIPS.html.

### Constants

REQUIRE_MUTEX

  A mutex for Digest().

### Public Class Methods

bubblebabble(string) → bubblebabble_string click to toggle source

Returns a BubbleBabble encoded version of a given string.

    static VALUE
    rb_digest_s_bubblebabble(VALUE klass, VALUE str)
    {
        return bubblebabble_str_new(str);
    }

hexencode(string) → hexencoded_string click to toggle source

Generates a hex-encoded version of a given string.

    static VALUE
    rb_digest_s_hexencode(VALUE klass, VALUE str)
    {
        return hexencode_str_new(str);
    }