动态异构冗余结构的拟态防御自动机模型

动态异构冗余结构是拟态防御技术的常用工程模型.然而,目前尚缺乏对该结构实施形式化分析的手段,因为该结构缺乏形式化建模方法.针对此问题,使用有穷状态自动机及其并行组合自动机为一些拟态攻防行为建立计算模型.首先,使用单个有穷状态自动机为单个执行体建模;其次,使用有穷状态自动机的并行组合为执行体组合建模;再次,修改状态迁移规则,得到可描述攻防行为的拟态防御自动机模型;最后,根据该自动机模型的状态条件,分析动态异构冗余结构上拟态攻防行为的安全性.此外,也可使用交替自动机为拟态攻防建模,并把安全性自动分析规约为交替自动机模型检测问题.     

离散时间区间时序逻辑可满足性的判定

目前还没有模型检查的方法自动检测模型是否满足时间区间时序逻辑描述的性质.我们约束时间域到离散时间,证明了离散时间区间时序逻辑的可满足性是可判定的,因而是可模型检查的.提出了时间正则图模型,通过从离散时间区间时序逻辑到时间正则图的构造,提出了基于该逻辑的判定算法,该算法可以推广到其它的时序逻辑模型检查,并优于现有的基于自动机的时序逻辑判定方法.     

时间自动机两种模型的构造互模拟研究

基于时间自动机不同模型的验证被工业界广泛应用，本文形式描述了两种这样的模型，给出了从事件时钟自动机到双向时间自动机的构造方法，证明了二者识别语言之间的包含关系。     

从线性时序逻辑公式到自动机的转换算法

To combat the well-known state-space explosion problem in Propositional Linear Temporal Logic (PLTL) model checking, a novel algorithm capable of translating PLTL formulas into Nondeterministic Automata (NA) in an efficient way is proposed. The algorithm firstly transforms PLTL formulas into their non-free forms, then it further translates the non-free formulas into their Normal Forms (NFs), next constructs Normal Form Graphs (NFGs) for NF formulas, and it finally transforms NFGs into the NA which accepts both finite words and infinite words. The experimental data show that the new algorithm reduces the average number of nodes of target NA for a benchmark formula set and selected formulas in the literature, respectively. These results indicate that the PLTL model checking technique employing the new algorithm generates a smaller state space in verification of concurrent systems.     

以DNA为载体的线性时序逻辑模型检测

线性时序逻辑模型检测被广泛应用于处理器设计与验证、网络协议验证、安全协议验证等领域.然而到目前为止,该技术只能在电子计算的平台上实现.为了以脱氧核糖核酸(Deoxyribo Nucleic Acid,DNA)为载体对线性时序逻辑(Linear Temporal Logic,LTL)实施模型检测,给出了使用粘贴自动机实现Until算子模型检测的方法.首先,使用粘贴自动机对Until公式的有穷状态自动机(Finite State Automata,FSA)模型进行编码;然后,将系统模型转换为粘贴自动机的输入字符串;最后,用粘贴自动机验证系统是否满足公式.仿真实验结果证实,新方法可实现对LTL逻辑时序算子的检测.     

一种基于区间时序逻辑模型检测的入侵检测算法

Model checking based on linear temporal logic reduces the false negative rate of misuse detection. However, linear temporal logic formulae cannot be used to describe concurrent attacks and piecewise attacks. So there is still a high rate of false negatives in detecting these complex attack patterns. To solve this problem, we use interval temporal logic formulae to describe concurrent attacks and piecewise attacks. On this basis, we formalize a novel algorithm for intrusion detection based on model checking interval temporal logic. Compared with the method based on model checking linear temporal logic, the new algorithm can find unknown succinct attacks. The simulation results show that the new method can effectively reduce the false negative rate of concurrent attacks and piecewise attacks.