A New Relay Attack on Distance Bounding Protocols and Its Solution with Time-Stamped Authentication for RFID

Relay attack is one of the most threatening challenges against radio frequency identification（RFID） now. Distance bounding protocols have been introduced to thwart relay attacks. They form a family of challenge-response authentication protocols and confirm the round-trip time at the Rapid Bit Exchange phase. They enable a reader to authenticate and to establish an upper bound on the physical distance to an entrusted tag. We design an effective attack against a family of such protocols to launch the spoofing attacks within effective distance successfully, which demonstrates that existing protocols cannot eliminate such attacks completely. The thesis proposes a new program with time- stamping verification to correct the defect and verify the effectiveness.

Improved lower bound for the complexity of unique shortest vector problem

Unique shortest vector problem(uSVP)plays an important role in lattice based cryptography.Many cryptographic schemes based their security on it.For the cofidence of those applications,it is essential to clarify the complex-ity of uSVP with different parameters.However,proving the NP-hardness of usVP appears quite hard.To the state of the art,we are even not able to prove the NP-hardness of usVP with constant parameters.In this work,we gave a lower bound for the hardness of usVP with constant parameters,i.e.we proved that uSVP is at least as hard as gap shortest vector problem(GapSVP)with gap of O(√n/log(n)),which is in NP n coAM.Unlike previous works,our reduction works for paramters in a bigger range,especially when the constant hidden by the big-O in GapsVP is smallerthan1.

Recognition of 3-D Aircrafts by Fourier Descriptors with Fast and Efficient Library Search

Fourier descriptors are used as features for 3-D aircraft classification and pose determination from a 2-D image recorded at an arbitrary viewing angle. By the feature ranking of Fourier descriptors, a classification procedure based on the fast nearest neighbour rule is proposed to save the matching time of an unknown aircraft with a partial library search. The testing results of some typical examples indicate this method is generally applicable and efficient in 3-D aircraft recognition.

Images of Linear Block Codes over F_(q)+uF_(q)+vF_(q)+uvF_(q)

In this paper, we considered linear block codes over Rq=Fq+uFq+vFq+uvFq, u2=v2=0,uv=vu where q=pm, m∈N . First we looked at the structure of the ring. It was shown that Rq is neither a finite chain ring nor a principal ideal ring but is a local ring. We then established a generator matrix for the linear block codes and equipped it with a homogeneous weight function. Field codes were then constructed as images of these codes by using a basis of Rq over Fq . Bounds on the minimum Hamming distance of the image codes were then derived. A code meeting such bounds is given as an example.

Energy analysis of stability of twin shallow tunnels based on nonlinear failure criterion

Based on nonlinear Mohr-Coulomb failure criterion, the analytical solutions of stability number and supporting force on twin shallow tunnels were derived using upper bound theorem of limit analysis. The optimized solutions were obtained by the technique of sequential quadratic programming. When nonlinear coefficient equals 1 and internal friction angle equals 0, the nonlinear Mohr-Coulomb failure criterion degenerates into linear failure criterion. The calculated results of stability number in this work were compared with previous results, and the agreement verifies the effectiveness of the present method. Under the condition of nonlinear Mohr-Coulomb failure criterion, the results show that the supporting force on twin shallow tunnels obviously increases when the nonlinear coefficient, burial depth, ground load or pore water pressure coefficients increase. When the clear distance is 0.5to 1.0 times the diameter of tunnel, the supporting force of twin shallow tunnels reaches its maximum value, which means that the tunnels are the easiest to collapse. While the clear distance increases to 3.5 times the diameter of tunnel, the calculation for twin shallow tunnels can be carried out by the method for independent single shallow tunnel. Therefore, 3.5 times the diameter of tunnel serves as a critical value to determine whether twin shallow tunnels influence each other. In designing twin shallow tunnels,appropriate clear distance value must be selected according to its change rules and actual topographic conditions, meanwhile, the influences of nonlinear failure criterion of soil materials and pore water must be completely considered. During the excavation process, supporting system should be intensified at the positions of larger burial depth or ground load to avoid collapses.