In order to solve the problems about identity authentication

privacy protection

dynamic shared-key updating and de-synchronization that emerged in mobile radio frequency identification (RFID) authentication protocols

the paper proposes a mutual authentication protocol of mobile RFID whose shared-key can be updated dynamically.Based on Hash cryptography

the proposed protocol uses pseudo-random number to perform simultaneous operations on secure shared-key updating and identity authenticating

then uses a method of dynamic deletion and addition of shared-key that respectively stored in current data table and historic data table to reserve the coherency of shared-key among backend server

reader and tag after the latest legal authentication.The securities and efficiencies analysis show that the protocol can achieve secure updates of dynamic shared-key

identity authentication and shared-key synchronization after being attacked

and in addition

the proposed protocol has strong computation and storage abilities.Compared with other similar mobile RFID protocols

the proposed protocol can make up for the deficiency of these protocols

which is suitable for RFID systems with a large number of passive tags.