模型学习与符号执行结合的安全协议代码分析技术

符号执行技术从理论上可以全面分析程序执行空间,但对安全协议这样的大型程序,路径空间爆炸和约束求解困难的局限性导致其在实践上不可行。结合安全协议程序自身特点,提出用模型学习得到的协议状态机信息指导安全协议代码符号执行思路;同时,通过将协议代码中的密码学逻辑与协议交互逻辑相分离,避免了因密码逻辑的复杂性导致路径约束无法求解的问题。在SSH协议开源项目Dropbear上的成功实践表明了所提方法的可行性;通过与 Dropbear 自带的模糊测试套件对比,验证了所提方法在代码覆盖率与错误点发现上均具有一定优势。     

基于图结构源代码切片的智能化漏洞检测系统

针对智能化漏洞检测,从源代码程序依赖图中根据漏洞特征提取图结构源代码切片,将图结构切片信息表征后利用图神经网络模型进行漏洞检测工作。实现了切片级的漏洞检测,并在代码行级预测漏洞行位置。为了验证系统的有效性,分别与静态漏洞检测系统、基于序列化文本信息和基于图结构化信息的漏洞检测系统做比较,实验结果表明,所提系统在漏洞检测能力上有较高准确性,并且在漏洞代码行预测工作上有较好表现。     

基于前向纠错的自适应网络传输机制

针对无线网络中的传输控制协议(TCP)因为丢包触发丢包重传机制而导致传输性能大幅下降的问题,提出了一种基于前向纠错的自适应传输机制(AdaptiveFEC).该机制通过前向纠错来减少数据段的丢失,以避免触发TCP的丢包重传机制,从而达到提升TCP传输性能的目的.首先,根据当前的网络状况以及当前连接的数据传输特征确定当前...     

Static scheduling for barrier MIMD architectures

In a SIMD or VLIW machine, conceptual synchronizations are accomplished by using a static code schedule that does not require run-time synchronization. The lack of run-time synchronization overhead makes these machines very effective for fine-grain parallelism, but they cannot execute parallel code structures as general as those executed by MIMD architectures, and this limits their utility.In this paper we present a timing analysis that allows a compiler for a MIMD machine to eliminate a large fraction of the run-time synchronization by making efficient use of static code scheduling. Although these techniques can be adapted to be applied to most MIMD machines, this paper centers on the analysis and scheduling for barrier MIMD machines. Barrier MIMDs are asynchronous multiple instruction stream/multiple data stream architectures capable of parallel execution of variable execution-time instructions and arbitrary control flow (e.g., while loops and calls). However, they also incorporate a special hardware barrier synchronization mechanism that facilitates static scheduling by providing a mechanism which the compiler can use to enforce precise timing constraints. In other words, the compiler tracks relative timing between processors and uses static code scheduling until the timing imprecision becomes too large, at which point the compiler simply inserts a barrier to reduce that timing imprecision to zero (or a small constant).This paper describes new scheduling and barrier placement algorithms for barrier MIMDs that are based loosely on the list scheduling approach employed for VLIWs [Ellis 1985]. In addition, the experimental results from scheduling thousands of synthetic benchmark programs for a parameterized barrier MIMD machine are presented.     

A singular loop transformation framework based on non-singular matrices

In this paper, we discuss a loop transformation framework that is based on integer non-singular matrices. The transformations included in this framework are called Λ-transformations and include permutation, skewing and reversal, as well as a transformation calledloop scaling. This framework is more general than existing ones; however, it is also more difficult to generate code in our framework. This paper shows how integer lattice theory can be used to generate efficient code. An added advantage of our framework over existing ones is that there is a simple completion algorithm which, given a partial transformation matrix, produces a full transformation matrix that satisfies all dependences. This completion procedure has applications in parallelization and in the generation of code for NUMA machines. This work was supported by the Cornell Theory Center, NSF Presidential Young Investigator award #CCR-8958543. by NSF Grant #CCR-9008526, and by a grant from the Hewlett-Packard Company.     

基于空间填充曲线的动态负载均衡算法

针对Web集群系统中服务器的数量不断增加、负载指标动态变化的特点,为实现均衡的分配请求,提出一种使用空间填充曲线来实现动态负载均衡的算法。利用空间填充曲线可高效得将高维数据映射到一维索引的特点,使均衡器根据实时收集的各项负载指标快速定位到最优编码的服务器。实验结果表明,该算法能有效地缩短请求响应时间,提升了集群系统的整体性能,在大规模集群系统中均衡效果更好。     

GaiaDoc： A Tool Focused on Business Requirements for Code Documentation with a CMMI Compliant and RUP Based on Requirement Flow

Aiming to fill a gap in traditional methods of source code documentation, which focus mainly on the API （application programming interface） documentation for other programmers, this article presents a new approach for business requirements, mapping them through a set of annotations. These annotations, in turn, are interpreted by the GaiaDoc tool, which is specified in this paper and is able to generate documentation in form of use case specifications in a language and format easily understandable by the project stakeholders. Along with the GaiaDoc tool proposal, a RUP （rational unified process） based requirements flow is developed to fit with its needs and it is validated through CMMI （capability maturity model integration） requirement process areas and a case study of the proposed methodology＇s application is presented before the final considerations.     

Design of a Rotary Ring APP Information Capturer for Sightseeing PlacemSpecialized Tourism Services for Sun-Moon Lake

The APP （Application） store at the Android market is very popular and attractive for most of current smart phone users. A rotary ring type of APP named as Loving SML （Loving Sun-Moon Lake--＂爱上日月谭＂） is an instant information capturer to capture the instant traffic tourism information （info） services and serve as an interactive device for user to know the instant traffic information of SML area where you may want to go. The tourism service is specialized on i3 travel, which is identified as innovation, intelligent, and interesting for all of the visitors coming from all over the world. The captured instant information is provided by the sightseeing cloud from SML-NSA （National Scenic Area） with the integration of infrastructure of VD （vehicle detector）, CMS or VMS （changeable （or variable） message sign）, CCTV （closed circuit television）, AVI （automatic vehicle identification）. The technique of AR （augmented reality） is also used to identify how many sparkling places in front of you that you may visit. One can easily know the road performance ahead from you before you plan a trip.     

油水两相流阵列电导探针测量电路设计

通过利用电导探针测量探头针尖处液体导电性的变化,确定该点的油水信息;本文详细介绍了阵列电导探针制作,设计了信号采集电路和极性转换电路硬件电路,采集的数据以曼彻斯特码的形式存储和传输,经实验验证效果良好.     

面向电力线通信的RA码自适应迭代译码方法

为降低信息在强干扰电力线信道中传输的误码率,对重复累积（RA）码的置信传播（BP）译码算法进行改进。修正BP译码算法中信息节点的初始值,利用自适应迭代译码减少译码过程中的迭代次数,并对译码进行预判决,降低了RA码译码复杂度、提高了译码效率。在Middleton A类电力线信道模型下仿真结果表明：改进后的译码方法在低信噪比区域与BP算法性能相近,而在较高信噪比区域改进后的算法与BP译码算法相比所需信噪比少约0.8 dB,并且显著减少了译码过程中的迭代次数。