This paper regards the RFID's security by analyzing the existing literature on these issues, with a critical point of view. The fast growth of Radio Frequency Identification (RFID) implies a deployment challenge, namely how to keep this technology scalable without renouncing security and privacy features, because these systems can easily create new threats to the security and privacy of individuals and organizations. Over the past few years, several streams of research have emerged approaching the RFID tag/reader privacy-security problem from different perspectives. This paper considers appropriate techniques and protocols that can fix security problems. It also points RFIDs cracking methods.