cryptor.rb

require 'openssl'
require 'base64'

class Cryptor
  def initialize
    @secret = "fd5d148867091d7595c388ac0dc50bb465052b764c4db8b4b4c3448b52ee0b33df16975830acca82"
    @cipher = OpenSSL::Cipher.new("AES-256-CFB")
  end

  def encrypt(*numbers)
    @cipher.encrypt
    @cipher.random_iv
    @cipher.key = @secret
    data = numbers.pack("Q*")
    encrypted = @cipher.update(data) + @cipher.final
    digest = OpenSSL::Digest::Digest.new('SHA1')
    signed = encrypted + OpenSSL::HMAC.digest(digest, @secret, encrypted)
    Base64.urlsafe_encode64(signed)
  end

  def decrypt(data)
    unencoded = Base64.urlsafe_decode64(data)
    encrypted = unencoded.slice!(0..(unencoded.length - 21))
    signature = unencoded
    digest = OpenSSL::Digest::Digest.new('SHA1')
    raise "Bad signature" unless signature == OpenSSL::HMAC.digest(digest, @secret, encrypted)

    @cipher.decrypt
    @cipher.key = @secret
    (@cipher.update(encrypted) + @cipher.final).unpack("Q*")
  end
end

cryptor = Cryptor.new
encrypted = cryptor.encrypt(9223372036854775800, 9223372036854775800)
puts "Encrypted is %d bytes" % encrypted.length
puts encrypted
puts cryptor.decrypt(encrypted).inspect