This module provides a framework for message digest libraries.

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

A cryptographic hash function is a procedure that takes data and return 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.


require 'digest'

# Compute a complete digest
sha256 = Digest::SHA256.new
digest = sha256.digest message

# Compute digest by chunks
sha256 = Digest::SHA256.new
sha256.update message1
sha256 << message2 # << is an alias for update

digest = sha256.digest

Digest algorithms

Different digest algorithms (or hash functions) are available :


See FIPS PUB 198 The Keyed-Hash Message Authentication Code (HMAC)


(as Digest::RMD160) see http://homes.esat.kuleuven.be/~bosselae/ripemd160.html


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: http://csrc.nist.gov/publications/PubsFIPS.html

Additionally Digest::BubbleBabble encodes a digest as a sequence of consonants and vowels which is more recognizable and comparable than a hexadecimal digest. See http://en.wikipedia.org/wiki/Bubblebabble

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