gistfile1.rb

class StreamCrypto
  def self.aes_ctr_encrypt(clear_text,nonce,key)
    counter=nonce.unpack('q')[0]
    keystream = ""
    cipher = OpenSSL::Cipher.new 'aes128'
    cipher.padding=0
    cipher.encrypt
    cipher.key=key
    (Float(clear_text.length)/key.length).ceil().times do  
      stream_nonce="\0"*8+[counter].pack('q')
      puts stream_nonce.inspect
      keystream += cipher.update(stream_nonce)
      counter+=1
    end
    return CryptoTools.xor_str(keystream.slice(0,clear_text.length),clear_text)
  end
  def self.aes_ctr_decrypt(cipher_text,nonce,key)
    aes_ctr_encrypt(cipher_text,nonce,key)
  end
end