md5self.rb

#!/usr/bin/env ruby

require 'digest/md5'

def random_hex(length)
  bytes_needed = (length + 1) / 2
  bytes = $urandom.read(bytes_needed)

  hex = ("%02x" * bytes_needed) % bytes.bytes
  return hex[0,length]
end

pids = []
(1..32).each do |size|
  pids << fork do
    $urandom = File.open("/dev/urandom")
    $0 = "md5self(#{size})"

    templates = nil
    if size == 32
      templates = [
        "the MD5 of this message is ",
        "the md5 of this message is ",
        "The MD5 of this message is ",
        "The md5 of this message is ",
        "this message's MD5 is ",
        "this message's md5 is ",
        "This message's MD5 is ",
        "This message's md5 is ",
        "this message has an MD5 of ",
        "this message has an md5 of ",
        "This message has an MD5 of ",
        "This message has an md5 of ",
      ]
    else
      templates = [
        "the MD5 of this message starts with ",
        "the md5 of this message starts with ",
        "The MD5 of this message starts with ",
        "The md5 of this message starts with ",
        "this message's MD5 starts with ",
        "this message's md5 starts with ",
        "This message's MD5 starts with ",
        "This message's md5 starts with ",
        "the MD5 of this message begins with ",
        "the md5 of this message begins with ",
        "The MD5 of this message begins with ",
        "The md5 of this message begins with ",
        "this message's MD5 begins with ",
        "this message's md5 begins with ",
        "This message's MD5 begins with ",
        "This message's md5 begins with ",
        "this message has an MD5 starting with ",
        "this message has an md5 starting with ",
        "This message has an MD5 starting with ",
        "This message has an md5 starting with ",
        "this message has an MD5 beginning with ",
        "this message has an md5 beginning with ",
        "This message has an MD5 beginning with ",
        "This message has an md5 beginning with ",
      ]
    end

    loop do
      wanted = random_hex(size)

      templates.each do |templ|
        message = templ + wanted
        actual = Digest::MD5.hexdigest(message)

        if actual.start_with?(wanted)
          puts message
          exit(0)
        end
      end
    end
  end
end

until pids.empty?
  pids.delete(Process.wait)
end