  In this paper, authentication for mobile radio frequency identification
(RFID) systems with low-cost tags is studied. Firstly, an adaptive modulus (AM)
encryption algorithm is proposed. Subsequently, in order to enhance the
security without additional storage of new key matrices, a self-updating
encryption order (SUEO) algorithm is designed. Furthermore, a diagonal block
local transpose key matrix (DBLTKM) encryption algorithm is presented, which
effectively expands the feasible domain of the key space. Based on the above
three algorithms, a novel joint AM-SUEO-DBLTKM encryption algorithm is
constructed. Making full use of the advantages of the proposed joint algorithm,
a two-way RFID authentication protocol, named AM-SUEO-DBLTKM-RFID, is proposed
for mobile RFID systems. In addition, the Burrows-Abadi-Needham (BAN) logic and
security analysis indicate that the proposed AM-SUEO-DBLTKM-RFID protocol can
effectively combat various typical attacks. Numerical results demonstrate that
the proposed AM-SUEO-DBLTKM algorithm can save 99.59\% of tag storage over
traditional algorithms. Finally, the low computational complexity as well as
the low storage cost of the proposed AM-SUEO-DBLTKM-RFID protocol facilitates
deployment within low-cost RFID tags.
