gistfile1.txt

def dm_crypt(message, key)
  if key.empty?
    return message
  end
  
  result = ""
  i = 0
  message.each_byte do |byte|
    result += (byte ^ key[i % key.bytesize].ord ^ i).chr
    i += 1
  end
  
  return dm_crypt(result, key[1..-1])
end

def dm_keygen(msg = nil)
  complexity = 2
  random = File.open("/dev/urandom")
  msg = random.read(complexity) unless msg
  base_key = random.read(complexity)
  result = dm_crypt(msg, base_key)

  Fiber.new do
    loop do
      File.open("/dev/null", "r+b").write(random.read(complexity * 16))
      key = random.read(complexity)
      while result != dm_crypt(msg, key)
        key = random.read(complexity)
      end
      Fiber.yield key
    end
  end
end