Verifying security protocols by knowledge analysis

This paper describes a new interactive method to analyse knowledge of participants involved in security protocols and further to verify the correctness of the protocols. The method can detect attacks and flaws involving interleaving sessions besides normal attacks. The implementation of the method in a generic theorem proving environment, namely Isabelle, makes the verification of protocols mechanical and efficient; it can verify a medium-sized security protocol in less than ten seconds. As an example, the paper finds the flaw in the Needham-Schroeder public key authentication protocol and proves the secure properties and guarantees of the protocol with Lowe's fix to show the effectiveness of this method

Enhanced sampling in generalized ensemble with large gap of sampling parameter: case study in temperature space random walk

We present an efficient sampling method for computing a partition function and accelerating configuration sampling. The method performs a random walk in the $\lambda$ space, with $\lambda$ being any thermodynamic variable that characterizes a canonical ensemble such as the reciprocal temperature $\beta$ or any variable that the Hamiltonian explicitly depends on. The partition function is determined by minimizing the difference of the thermal conjugates of $\lambda$ (the energy in the case of $\lambda=\beta$), defined as the difference between the value from the dynamically updated derivatives of the partition function and the value directly measured from simulation. Higher-order derivatives of the partition function are included to enhance the Brownian motion in the $\lambda$ space. The method is much less sensitive to the system size, and the size of $\lambda$ window than other methods. On the two dimensional Ising model, it is shown that the method asymptotically converges the partition function, and the error of the logarithm of the partition function is much smaller than the algorithm using the Wang-Landau recursive scheme. The method is also applied to off-lattice model proteins, the $AB$ models, in which cases many low energy states are found in different models.Comment: 7 pages, 3 figure

Zero-error Slepian-Wolf Coding of Confined Correlated Sources with Deviation Symmetry

In this paper, we use linear codes to study zero-error Slepian-Wolf coding of a set of sources with deviation symmetry, where the sources are generalization of the Hamming sources over an arbitrary field. We extend our previous codes, Generalized Hamming Codes for Multiple Sources, to Matrix Partition Codes and use the latter to efficiently compress the target sources. We further show that every perfect or linear-optimal code is a Matrix Partition Code. We also present some conditions when Matrix Partition Codes are perfect and/or linear-optimal. Detail discussions of Matrix Partition Codes on Hamming sources are given at last as examples.Comment: submitted to IEEE Trans Information Theor

Strategic investment and excess capacity: A study of the Taiwanese flour industry.

The Taiwanese flour industry’s capacity utilization rate has maintained an extremely low level of 40% for more than 20 years. This article sets up a two-stage game model and uses the strategic effect of the firm’s capital investment on its rivals’ outputs to explain the nature of this excess capacity. The model is tested with panel data from the Taiwanese flour industry by using non-linear three-stage least squares. The evidences indicate that a large capacity built in the past could have been used strategically to reduce other firms’ outputs, in the context of a concerted action among the incumbent firms.strategic investment, two-stage game, collusion, conjectural variation