Radio frequency identification (RFID) technology is expected to become an important and ubiquitous infrastructure technology of supply chain processes and customer service. The low-cost tag, or so-called passive tag, will be likely the factor for widespread adoption of the technology. It must be noticed that the deployment of such tags may create new threats to user privacy due to the powerful tracking capability of the tags. As a result, some sort of security issues must be imposed on the passive tags for addressing the privacy problem. However, providing security in such tags is a challenging task because they are highly resource constrained and cannot support strong cryptography. This paper provides both discussion on the requirements and restrictions of security implementation of a RFID system. It also examines the features and issues pertinent to several existing RFID security solution. Finally, this paper suggests the use of our proposed lightweight security protocol based on Ohkubo [1]?s scheme, which protects user privacy using a hash chain mechanism and also provides an analysis of the protocol.