ruby-hmac: HMAC for Ruby

This module provides a common interface to HMAC functionality.  HMAC
is a kind of "Message Authentication Code" (MAC) algorithm which
standard is documented in RFC2104.  Namely, a MAC provides a way to
check the integrity of information transmitted over or stored in an
unreliable medium, based on a secret key.

WWW: http://deisui.org/~ueno/ruby/hmac.html