hamming.rb

#!/usr/bin/env ruby
require 'digest/sha1'
require 'rubygems'
require 'amatch'
require 'bio'

challenge_phrase = File.read('challenge.txt')
challenge_sha1   = Digest::SHA1.hexdigest(challenge_phrase)
words            = File.read('dict.txt').split("\n").uniq
test_phrase      = words.sort{rand <=> 0.5}[3..rand(10)+5].join(' ')
threshold        = 29
cycles           = 1000000

cycles.times do |x|
  randomness = ('a'..'z').sort{rand <=> 0.5}[0..5].join
  5.times do |r|
    phrase = test_phrase + randomness[0..r]
    test_phrase_sha1 = Digest::SHA1.hexdigest(phrase)
    m = Amatch::Hamming.new(test_phrase_sha1)
    offset = m.match(challenge_sha1).to_s
   if offset.to_i <= threshold
      puts "'#{phrase}' => #{offset}"
   end
  end
  puts '.' if x % 1000 == 0
end

In response to http://www.engineyard.com/blog/2009/programming-contest-win-iphone-3gs-2k-cloud-credit/