椭圆曲线数字签名算法(elliptic curve digital signature algorithm,ECDSA)是应用最广的数字签名算法之一,在签名过程中需要计算椭圆曲线上的标量乘法,该操作通常是签名中最耗时的部分.在目前许多密码库的实现中都使用非相邻窗口形式...椭圆曲线数字签名算法(elliptic curve digital signature algorithm,ECDSA)是应用最广的数字签名算法之一,在签名过程中需要计算椭圆曲线上的标量乘法,该操作通常是签名中最耗时的部分.在目前许多密码库的实现中都使用非相邻窗口形式表示临时密钥,从而减少标量乘法的计算时间,但是也使得攻击者能够通过侧信道攻击获取临时密钥的部分信息,恢复签名密钥.使用扩展隐藏数问题提取侧信道轨迹中的信息,并通过格攻击恢复密钥,是针对ECDSA的主流攻击框架之一.基于此,提出了3方面的优化方法:1)邻域动态约束合并策略.通过动态的合并参数可以降低格的维数,并控制攻击过程中已知信息的损失量,使得对于任意的签名均能够以很高成功率恢复密钥.2)对于格中嵌入数进行分析与优化,使得目标向量的欧几里得范数减少约8%,有效提高了攻击的成功率并减少了时间开销.3)提出了一种线性断言方法,能够显著降低格筛法的时间开销.在使用2个签名的情况下以0.99的成功率恢复签名密钥.展开更多
A novel algorithm for Bayesian document segmentation is proposed based on the wavelet domain hidden Markov tree (HMT) model. Once the parameters of model are known, according to the sequential maximum a posterior prob...A novel algorithm for Bayesian document segmentation is proposed based on the wavelet domain hidden Markov tree (HMT) model. Once the parameters of model are known, according to the sequential maximum a posterior probability (SMAP) rule, firstly, the likelihood probability of HMT model for each pattern is computed from fine to coarse procedure. Then, the interscale state transition probability is solved using Expectation Maximum (EM) algorithm based on hybrid-quadtree and multiscale context information is fused from coarse to fine procedure. In order to get pixel-level segmentation, the redundant wavelet domain Gaussian mixture model (GMM) is employed to formulate pixel-level statistical property. The experiment results show that the proposed scheme is feasible and robust.展开更多
Many kinds of channel currents are especially weak and the background noise dominates in the patch clamp recordings. This makes the threshold detection fail during estimating of the transition probabilities. So direct...Many kinds of channel currents are especially weak and the background noise dominates in the patch clamp recordings. This makes the threshold detection fail during estimating of the transition probabilities. So direct fitting of the patch clamp recording, not of the histogram coming from the recordings, is a desirable way to estimate the transition probabilities. Iterative batch EM algorithm based on hidden markov model has been used in this field but which has the "curse of dimensionality" and besides cant keep tracking the varying of the parameters. A new on line sequential iterative one is proposed here, which needs fewer computational efforts and can adaptively keep tracking the varying of parameters. Simulations suggest its robust, effective and convenient.展开更多
论文在传统一阶隐马尔可夫模型的基础上,针对隐马尔可夫模型结构信息挖掘不全面的问题,提出了一种双层隐马尔可夫模型。双层隐马尔可夫模型在使用Baum-Welch算法的过程中将词性序列视为观测序列,通过Baum-Welch算法提取更多信息并最大...论文在传统一阶隐马尔可夫模型的基础上,针对隐马尔可夫模型结构信息挖掘不全面的问题,提出了一种双层隐马尔可夫模型。双层隐马尔可夫模型在使用Baum-Welch算法的过程中将词性序列视为观测序列,通过Baum-Welch算法提取更多信息并最大化词性序列概率从而更加贴合实际情况,同时对Viterbi算法做了相应的改动。模型在Penn Treebank语料库和Groningen Meaning Bank语料库上进行10折交叉验证,并与传统一阶、二阶隐马尔可夫模型进行对比。结果表明双层隐马尔可夫模型相较传统一阶、二阶隐马尔可夫模型词性标注正确率更高。展开更多
基金国家自然科学基金(the National Natural Science Foundation of China under Grant No.50279041)陕西省自然科学基金(the Natural Science Foundation of Shaanxi Province of China under Grant No.2005F07)。
文摘椭圆曲线数字签名算法(elliptic curve digital signature algorithm,ECDSA)是应用最广的数字签名算法之一,在签名过程中需要计算椭圆曲线上的标量乘法,该操作通常是签名中最耗时的部分.在目前许多密码库的实现中都使用非相邻窗口形式表示临时密钥,从而减少标量乘法的计算时间,但是也使得攻击者能够通过侧信道攻击获取临时密钥的部分信息,恢复签名密钥.使用扩展隐藏数问题提取侧信道轨迹中的信息,并通过格攻击恢复密钥,是针对ECDSA的主流攻击框架之一.基于此,提出了3方面的优化方法:1)邻域动态约束合并策略.通过动态的合并参数可以降低格的维数,并控制攻击过程中已知信息的损失量,使得对于任意的签名均能够以很高成功率恢复密钥.2)对于格中嵌入数进行分析与优化,使得目标向量的欧几里得范数减少约8%,有效提高了攻击的成功率并减少了时间开销.3)提出了一种线性断言方法,能够显著降低格筛法的时间开销.在使用2个签名的情况下以0.99的成功率恢复签名密钥.
文摘A novel algorithm for Bayesian document segmentation is proposed based on the wavelet domain hidden Markov tree (HMT) model. Once the parameters of model are known, according to the sequential maximum a posterior probability (SMAP) rule, firstly, the likelihood probability of HMT model for each pattern is computed from fine to coarse procedure. Then, the interscale state transition probability is solved using Expectation Maximum (EM) algorithm based on hybrid-quadtree and multiscale context information is fused from coarse to fine procedure. In order to get pixel-level segmentation, the redundant wavelet domain Gaussian mixture model (GMM) is employed to formulate pixel-level statistical property. The experiment results show that the proposed scheme is feasible and robust.
文摘Many kinds of channel currents are especially weak and the background noise dominates in the patch clamp recordings. This makes the threshold detection fail during estimating of the transition probabilities. So direct fitting of the patch clamp recording, not of the histogram coming from the recordings, is a desirable way to estimate the transition probabilities. Iterative batch EM algorithm based on hidden markov model has been used in this field but which has the "curse of dimensionality" and besides cant keep tracking the varying of the parameters. A new on line sequential iterative one is proposed here, which needs fewer computational efforts and can adaptively keep tracking the varying of parameters. Simulations suggest its robust, effective and convenient.
文摘论文在传统一阶隐马尔可夫模型的基础上,针对隐马尔可夫模型结构信息挖掘不全面的问题,提出了一种双层隐马尔可夫模型。双层隐马尔可夫模型在使用Baum-Welch算法的过程中将词性序列视为观测序列,通过Baum-Welch算法提取更多信息并最大化词性序列概率从而更加贴合实际情况,同时对Viterbi算法做了相应的改动。模型在Penn Treebank语料库和Groningen Meaning Bank语料库上进行10折交叉验证,并与传统一阶、二阶隐马尔可夫模型进行对比。结果表明双层隐马尔可夫模型相较传统一阶、二阶隐马尔可夫模型词性标注正确率更高。
