Local margin based semi-supervised discriminant embedding for visual recognition

Most manifold learning algorithms adopt the k nearest neighbors function to construct the adjacency graph. However, severe bias may be introduced in this case if the samples are not uniformly distributed in the ambient space. In this paper a semi-supervised dimensionality reduction method is proposed to alleviate this problem. Based on the notion of local margin, we simultaneously maximize the separability between different classes and estimate the intrinsic geometric structure of the data by both the labeled and unlabeled samples. For high-dimensional data, a discriminant subspace is derived via maximizing the cumulative local margins. Experimental results on high-dimensional classification tasks demonstrate the efficacy of our algorithm.     

An anonymous two-factor authenticated key agreement scheme for session initiation protocol using elliptic curve cryptography

The Session Initiation Protocol (SIP) is a signaling protocol widely applied in the world of multimedia communication. Numerous SIP authenticated key agreement schemes have been proposed with the purpose of ensuring security communication. Farash recently put forward an enhancement employing smart cards counted on Zhang et al.’s scheme. In this study, we observe that the enhanced scheme presented by Farash has also some security pitfalls, such as disclosure of user identity, lack of a pre-authentication in the smart card and vulnerability to key-compromise masquerading attack which results in an off-line guessing attack. We then propose an anonymous modified scheme with elliptic curve cryptography to eliminate the security leakages of the scheme proposed by Farash. We demonstrate that our scheme is immune to different kinds of attacks including attacks involved in Farash’s scheme. We mention Burrows-Abadi-Needham logic for completeness of the proposed scheme. Also, we compare the performance of our scheme with its predecessor schemes and the comparative results shows that it perfectly satisfies the needs of SIP.     

Hadamard quantum broadcast channels

We consider three different communication tasks for quantum broadcast channels, and we determine the capacity region of a Hadamard broadcast channel for these various tasks. We define a Hadamard broadcast channel to be such that the channel from the sender to one of the receivers is entanglement-breaking and the channel from the sender to the other receiver is complementary to this one. As such, this channel is a quantum generalization of a degraded broadcast channel, which is well known in classical information theory. The first communication task we consider is classical communication to both receivers, the second is quantum communication to the stronger receiver and classical communication to other, and the third is entanglement-assisted classical communication to the stronger receiver and unassisted classical communication to the other. The structure of a Hadamard broadcast channel plays a critical role in our analysis: The channel to the weaker receiver can be simulated by performing a measurement channel on the stronger receiver’s system, followed by a preparation channel. As such, we can incorporate the classical output of the measurement channel as an auxiliary variable and solve all three of the above capacities for Hadamard broadcast channels, in this way avoiding known difficulties associated with quantum auxiliary variables.     

多媒体数字产品版权保护模型研究与设计

非法的盗版行为侵害了创作者的合法权益,使得多媒体信息的版权保护问题变得十分重要。通过分析一般的版权保护管理系统,提出了一种有效保护多媒体信息版权的模型。该模型综合利用鲁棒水印和脆弱水印对多媒体信息进行4次水印嵌入;采用全文件加密的方式对多媒体信息加密;使用基于双缓冲机制及安全存储机制的专门的客户端软件对信息解密。最后通过性能分析可知,在没有降低系统的权威性、公平性、实用性的前提下,该模型提高了整个DRM系统的安全性。     

Cryptanalysis of an identity based broadcast encryption scheme without random oracles

Identity based broadcast encryption allows a centralized transmitter to send encrypted messages to a set of identities S, so that only the users with identity in S can decrypt these ciphertexts using their respective private key. Recently [Information Processing Letters 109 (2009)], an identity-based broadcast encryption scheme was proposed (Ren and Gu, 2009) [1], and it was claimed to be fully chosen-ciphertext secure without random oracles. However, by giving a concrete attack, we indicate that this scheme is even not chosen-plaintext secure.     

并发计算重复问题与控制方法

数据竞争问题是并发程序开发与测试难题,发现数据竞争可能导致计算重复,重复会导致系统性能下降.从实例出发定义了并发计算重复问题(concurrent computation redundancy problem,简称CCRP),给出了相关性能指标和判断方法,设计了通用并发重复控制机制.并发程序一般都可以基于生产者-消费者模型进行CCRP分析.以带数据源的生产者-消费者为例详细分析了CCRP,给出了单条件、条件交叉两种重复控制算法,算法具有不同的适用范围,都可以作为固定模式来解决CCRP,基于Petri网作了相关性质的证明与仿真.并发程序实验结果说明了并发重复控制的必要性和有效性,比较了两种算法的差异.该研究对于数据竞争检测、并发程序设计具有参考价值.     

IMS网络中的SIP洪泛攻击检测

为了检测针对3G核心网中IP多媒体子系统的SIP(session initiation protocol)洪泛攻击,提出了一种双抽样多点检测方法.该方法在使用计数式布鲁姆过滤器统计检测特征信息的基础上,将检测空间划分为5个范围,即正常范围、关注范围、检测范围、精检测范围和攻击范围,然后对落在不同范围内的统计信息给予相应...     

语义相似哈希构建语义DHT网络

传统的结构化对等网络以分布式哈希表(DHT)为核心,只支持基于特定关键字的精确搜索,不支持语义搜索.而为支持语义搜索而提出的语义DHT网络存在路由层次多、查准率低等问题.为此,基于标准α稳定分布提出了语义相似哈希对Chord节点上资源进行标识符分配,使语义相似资源具有相近的标识符,从而可将语义相似资源存放在Chord中相同或相近的节点上,实现对语义搜索的支持.仿真结果表明,使用语义相似哈希分配资源标识符的Chord网络可以在1.07%的节点范围实现70%查全率和80%的查准率,在单层拓扑上实现了语义搜索功能.     

面向SNS用户访问行为的Web缓存预测替换

为了提高web缓存性能,在已有缓存替换算法的基础上加入预测机制,提出了一种面向社交网站(SNS)用户访问行为特征的预测替换算法.通过研究SNS的用户行为模型,引入预测对象集,减小了替换风险,提高了缓存命中率.为了验证所提算法的性能,进行了大量仿真实验,结果表明,该算法在基于SNS使用行为的缓存方面,具有提高命中率的优越性.