Detect and identify blocker tags in tree-based RFID systems

Blocker tags are initially introduced to protect regular tags in certain ID ranges, called blocking ranges, from unwanted scanning in RFID systems. But if misused, blocker tags can cause blocking attacks that corrupt the communication between interfered regular tags and readers. Previous approaches can only detect blocking behavior. However, they cannot distinguish malicious blocking from legitimate blocking that can be perfectly allowed to protect customer's privacy. To solve the problem, we carry out the first attempt in the paper to detect real blocking attacks by identifying malicious blocking ranges from authorized ones in a system. We present two pioneer probe-based protocols that can accurately identify malicious blocking ranges in popular tree-based RFID systems, and get rid of their impact before performing RFID applications. We validate the efficacy of the two protocols through theoretical analysis and simulation experiments. The results show that our protocols can identify blocking ranges very fast even when the blocker tag percentage is very low, for example, dozens of blocker tags among tens of thousands of regular tags. Our protocols deliver also a faster blocker tag detection than previous detection methods; our best protocol reduces detection time by over 90% compared with the state-of-the-art detection method.