class Rack::Protection::SessionHijacking

def accepts?(env)
  session = session env
  key     = options[:tracking_key]
  if session.include? key
    session[key].all? { |k,v| v == encrypt(env[k]) }
  else
    session[key] = {}
    options[:track].each { |k| session[key][k] = encrypt(env[k]) }
  end
end