Fig. 1. Scheme of the coverage of a set of readers. The numbers are used to indicate different tag location situations.

Fig. 2. Communication graph.

Fig. 3. Diagram of Juels–Weis improved randomized hash locks.

Fig. 4. Messages generated upon the arrival of an authenticated tag into the system.

Fig. 5. Graphical scheme of the arrival of an authenticated tag into the system.

Fig. 6. Graphical scheme of an authenticated tag roaming about the system.

Fig. 7. Messages generated during the roaming protocol.

Fig. 8. Messages generated during the departure protocol.

Fig. 9. Graphical scheme of a tag departing through a SEP.

Fig. 10. The three test scenarios. From left to right “Empty”, “Unstructured” and “Corridor”.

Fig. 11. Evolution of the Cache/Total Ratio mean and deviation for different values of the roaming probability.

Fig. 12. Evolution of the Cache/Total Ratio mean and deviation for different values of the number of entering tags per step.

Fig. 13. Number of tags in each cache for the “Empty” scenario at steps 20 (left) and 300 (right).

Fig. 14. Number of tags in each cache for the “Unstructured” scenario at steps 20 (left) and 300 (right).

Fig. 15. Number of tags in each cache for the “Corridor” scenario at steps 20 (left) and 300 (right).

Symbols used in the architecture description

Message types used by the information sharing protocol suite