Improved Anonymity for Key-Trees

Randomized hash-lock protocols for Radio Frequency IDentification (RFID) tags offer forward untraceability, but incur heavy search on the server. Key trees have been proposed as a way to reduce search times, but because partial keys in such trees are shared, key compromise affects several tags. Buttyän et al. have quantified the resulting loss of anonymity in the system, and proposed specific tree properties in an attempt to minimize this loss. We will further improve upon these results, and provide a proof of optimality. Finally, our proposals are compared to existing results by means of simulation

Improved Anonymity for Key-trees

Randomized hash-lock protocols for Radio Frequency IDentification (RFID) tags offer forward untraceability, but incur heavy search on the server. Key trees have been proposed as a way to reduce search times, but because partial keys in such trees are shared, key compromise affects several tags. Butty´an et al. have defined measures for the resulting loss of anonymity in the system, and approximated their measures by means of simulations. We will further improve upon their trees, and provide a proof of optimality. Finally, an efficient recursive algorithm is presented to compute the anonymity measures