crypto.rb

require 'openssl'

module Crypto
  module_function

  def encrypt(iv, data)
    enc = OpenSSL::Cipher::AES256.new(:CBC)
    enc.encrypt
    enc.key = key_with_padding(iv)
    (enc.update(data) + enc.final).unpack("H*").first
  end

  def decrypt(iv, data)
    dec = OpenSSL::Cipher::AES256.new(:CBC)
    dec.decrypt
    dec.key = key_with_padding(iv)
    (dec.update(Array.new([data]).pack("H*")) + dec.final)
  end

  def key_with_padding(iv)
    padding = "\x00" * (32 - iv.size)
    return (iv + padding).encode(Encoding::BINARY)
  end
end