A Cross Layer Protocol for Fast Identification of Blocked Tags in Large-scale RFID Systems

Blocker tag attack is one of the denial-of-service (DoS) attacks that threatens the privacy and security of RFID systems. The attacker interferes with the blocked tag by simulating a fake tag with the same ID, thus causing a collision of message replies. In many practical scenarios, the number of blocked tags may vary, or even be small. For example, the attacker may only block the important customers or high-value items. To avoid the disclosure of privacy and economic losses, it is of great importance to fast pinpoint these blocked ones. However, existing works do not take into account the impact of the number of blocked tags on the execution time and suffer from incomplete identification of blocked tags, long identification time or privacy leakage. To overcome these limits, we propose a cross layer blocked tag identification protocol (CLBI). CLBI consists of multiple rounds, in which it enables multiple unblocked tags to select one time slot and concurrently verify them by using tag estimation in physical layer. Benefiting from the utilization of most collision slots, the execution time can be greatly reduced. Furthermore, for efficient identification of blocked tags under different proportions, we propose a hybrid protocol named adaptive cross layer blocked tag identification protocol (A-CLBI), which estimates the remaining blocked tag in each round and adjusts the identification strategy accordingly. Extensive simulations show that our protocol outperforms state-of-the-art blocked tags identification protocol.