Radio frequency identification (RFID) uses radio waves to identify any object, through the RFID tag identifier number. This book focuses on ultra-lightweight authentication protocols. Hung-Yu Chien classifies the authentication protocol into four classes; the proposed protocol is of the fourth class which provides a strong authentication and a strong integrity (SASI). Book introduces analysis and implements for SASI protocol and the two attacks. The outcome of this test is that the two attacks de-synchronize and break the protocol. By implementing and applying the two attacks to the proposed modification methodology, the outcome is that it failed to break the modified protocol. As a conclusion of our proposed modifications: The modifications led to more secured communication channels between the tag and the reader, which makes RFID systems counteract different de-synchronization attacks. The communication for the modified protocol is more secured than the unmodified SASI while is still at the same cost. There is a slight increasing in the storage overhead, but it's in the accepted ranges, which is compatible with the storage capabilities of RFID Tags."