可信平台模块的形式化分析和测试

可信平台模块(Trusted Platform Module,TPM)是可信计算平台的核心和基础,可信平台模块的功能测试和验证是保证可信平台模块的实现正确性以及规范一致性的重要手段,但是目前尚不存在一种有效严格的可信平台模块测试和功能验证方法,同时可信计算组织给出的TPM规范是描述性的,不利于产品的开发和测试.文中在分析可信平台模块目前存在的一些问题的基础上,以TPM密码子系统为例给出了该子系统的形式化规格说明,并且基于该规格说明,给出了扩展有限状态机模型,最后,将该有限状态机模型应用于测试用例的自动生成,并通过实验验证了形式化测试的有效性.

可信平台模块分析与测试技术研究

在可信计算平台的体系结构中，可信平台模块的基础性地位决定了其在可信计算平台的研究中居于中心的地位。本文对可信平台模块中可信机制特别是隐私性保护机制进行了详细的分析，并以可信平台模块作为建模的对象，对其进行形式化分析，探讨利用形式化模型生成测试用例，进行符合性测试的技术。本文主要取得了以下几个方面的成果： 1、针对现有的隐私性保护方案即BCC方案在多信任域环境下的不足，提出了一种多信任域内的直接匿名证明方案，该方案为直接匿名证明方案在多信任域的网络环境下的应用奠定了基础。 2、针对BCC方案匿名性机制中“验证着相关的完全或无”匿名性的缺陷，提出了带子群隐私保护的隐私性保护方案，该方案为小群体内应用隐私性保护方案提供了可行的解决方法，增强了现有隐私性保护方案匿名机制的灵活性。 3、提出了一种新的基于双线性映射的直接匿名证明方案，该方案的计算量小，签名长度短，为下一代基于椭圆曲线的可信平台模块提供了可行的隐私性保护方案。 4、针对目前可信平台模块符合性测试缺少自动化测试方案的现实，本文提出了一个新的针对可信平台模块的测试方案，该方案利用EFSM形式化模型生成测试用例，支持覆盖度的分析，可以实现测试的自动化，在符合性测试中可以帮助提高测试的覆盖程度与工作效率。 5、最后，本文首次对可信平台模块的本地化产品可信密码模块进行了系统的分析，指出了其中的AP授权协议的一些缺陷，并给出了改进意见，对可信密码模块和可信平台模块进行了详细的对比和分析，指出可信密码模块存在的不足和优势。 总的说来，本文的研究成果为可信平台模块的推广提供了有力的支撑，并且为我国可信密码模块的发展提供了借鉴。 关键词：可信平台模块、可信计算平台、 符合性测试、直接匿名证明

an integrity assurance mechanism for run-time programs

Chinese Assoc Cryptol Res, State Key Lab Informat Secur, Inst Software, Grad Univ Chinese Acad Sci, Natl Nat Sci Fdn China

基于可信平台的安全审计日志

任何的安全系统，审计日志都是非常重要的一部分．因此必须保护好审计日志，保证审计日志的保密性和完整性．安全审计日志机制就是为了保护日志系统自身的安全性的，Schneier和Kelsey提出了一种机制来实现日志的防篡改，可以很好地保护系统生成的日志，但是该机制需要依赖于可信服务器．初步探索了可信平台上的安全审计日志机制，并且提出了一种新的日志机制来保护可信平台上生成的日志．该日志机制建立在微软提出的NGSCB平台上，不需要依赖于可信服务器．

基于可信平台的一种访问控制策略框架——TXACML

根据可信平台访问控制需求,提出一个可信平台属性分类规则,定义属性评估函数,可以实现可信平台数据安全分发和访问.同时针对XACML现有的策略合成算法不能有效满足可信平台自动方策略复合需求,设计了一个基于平台可信度的策略合成算法,该算法可以使策略的优先级和可信度保持一致,实现自动方策略复合.在此基础上,进一步对XACML实施扩展,形成可信平台策略语言框架TXACML(XACML based on trusted platform).采取TXACML对一个实例给出了策略描述和策略合成过程,验证了TXACML的有效性.

可信密码模块符合性测试方法研究

提出了一种可信密码模块(TCM)符合性测试的形式化方法,采用基于扩展有限状态机(EFSM)模型与测试向量相结合的方式对TCM的标准进行形式化建模.由于该建模方法结合TCM自身特点给出了命令依赖关系图的获取算法以及EFSM模型与测试向量获取算法,所以能够更好地对标准进行形式化建模,并用于测试用例的产生.通过测试结果分析以及与其他相关工作的对比,表明该方法能够有效地产生测试用例,并提高TCM符合性测试的错误检测率.

Finite Element Analysis of Deformed Legs of Offshore Platform Structures

The element stiffness matrix of the equivalent beam or pipe element of the deformed leg of the platform is derived by the finite element method. The stresses and displacements of some damaged components are calculated, and the numeri-cal solutions agree well with those obtained by the fine mesh finite element method. Finally, as an application of this method, the stresses of some platform structures are calculated and analyzed.

Governing Equations and Numerical Solutions of Tension Leg Platform with Finite Amplitude Motion

It is demonstrated that when tension leg platform (TLP) moves with finite amplitude in waves, the inertia force, the drag force and the buoyancy acting on the platform are nonlinear functions of the response of TLP. The tensions of the tethers are also nonlinear functions of the displacement of TLP. Then the displacement, the velocity and the acceleration of TLP should be taken into account when loads are calculated. In addition, equations of motions should be set up on the instantaneous position. A theoretical model for analyzing the nonlinear behavior of a TLP with finite displacement is developed, in which multifold nonlinearities are taken into account, i.e., finite displacement, coupling of the six degrees of freedom, instantaneous position, instantaneous wet surface, free surface effects and viscous drag force. Based on the theoretical model, the comprehensive nonlinear differential equations are deduced. Then the nonlinear dynamic analysis of ISSC TLP in regular waves is performed in the time domain. The degenerative linear solution of the proposed nonlinear model is verified with existing published one. Furthermore, numerical results are presented, which illustrate that nonlinearities exert a significant influence on the dynamic responses of the TLP.

The W-11-4A platform comprehensive strength monitoring system

A comprehensive strength monitoring system used on a fixed jacket platform is presented in this paper. The long-term monitoring of W-11-4A platform achieved. Structural responses (strain and acceleration) at selected locations, as well as associated environmental parameters, have been obtained. The emphasis of the paper is placed on the system design, and the instrumentation and operation methodology employed in the monitoring of the structural responses. The performance of the system and the characteristic results obtained during its 13-month operation are also summarized.

Hill Instability Analysis Of Tlp Tether Subjected To Combined Platform Surge And Heave Motions

This paper presents the Hill instability analysis of Tension Leg Platform (TLP) tether it, deep sea. The 2-D nonlinear beam model which is Undergoing Coupled axial and transverse vibrations, is applied. The governing equations are reduced to nonlinear Hill equation by use of the Galerkin's method and the modes superposition principle. The Hill instability charted Lip to large parameters is obtained. An important parameter M is defined and can he expressed as the functions of tether length, the platform surge and heave motion amplitudes. Some example studies are performed for various environmental conditions. The results demonstrate that the nonlinear coupling between the axial and transverse vibrations has a significant effect on the response of structure.. It needs to be considered for the accurate dynamic analysis of long TLP tether subjected to the combined platform surge and heave motions.

Nonlinear analysis of pile foundation jacket platform

In this paper, the nonlinear collapse of the BOHAI-8 pile foundation jacket platform has been analyzed. The ultimate load and collapse process of two computational models of the structure are given. One model is of fixed support whose length is eight times the pile leg diameter and the other considers the nonlinearity of the soil-pile interaction.

Nonlinear Dynamic Response of Tension Leg Platform

Tension Leg Platform (TLP) is a typical compliant offshore structure for oil exploitation in deep water. Most of the existing mathematical models for analyzing the dynamic response of TLP are based on explicit or implicit assumptions that displacements (translations and rotations) are small magnitude. Herein a theoretical method for analyzing the nonlinear dynamic behavior of TLP with finite displacement is developed, in which multifold nonlinearities are taken into account, i.e. finite displacement, coupling of the six degrees of freedom, instantaneous position, instantaneous wet surface, free surface effects and viscous drag force. Using this theoretical model, we perform the numerical analysis of dynamic response of a representative TLP. The comparison between the degenerative linear solution of the proposed nonlinear model and the published one shows good agreements. Furthermore, numerical results are presented which illustrate that nonlinearities exert a distinct influence on the dynamic responses of the TLP.

Short-Term Nonlinear Response of Tension Leg Platform in Random Sea Waves

Most of the existing mathematical models for analyzing the dynamic response of TLP are based on explicit or implicit assumptions that motions (translations and rotations) are small magnitude. However, when TLP works in severe adverse conditions, the a priori assumption on small displacements may be inadequate. In such situation, the motions should be regarded as finite magnitude. This paper will study stochastic nonlinear dynamic responses of TLP with finite displacements in random waves. The nonlinearities considered are: large amplitude motions, coupling the six degrees-of-freedom, instantaneous position, instantaneous wet surface, free surface effects and viscous drag force. The nonlinear dynamic responses are calculated by using numerical integration procedure in the time domain. After the time histories of the dynamic responses are obtained, we carry out cycle counting of the stress histories of the tethers with rain-flow counting method to get the stress range distribution.

Parametric studies of tension leg platform with large amplitude motions

Tension leg platform (TLP) is an important kind of working station for deep water exploration and development in ocean, whose dynamic responses deserve a serious thought. It is shown that for severe sea state, the effects of nonlinearities induced by large displacements of TLP may be noteworthy, and then employment of small displacements model should be restrained. In such situation, large amplitude motion model may be an appropriate alternative. The numerical experiments are performed to study the differences of dynamic responses between the two models. It is shown that for most cases, differences between results of the two models are significant. The variances of the differences vs. the wave period are the most remarkable, and that of the differences vs. wave heading angle are also apparent.

Experimental Research On Fatigue Property Of Steel Rubber Vibration Isolator For Offshore Jacket Platform In Cold Environment

Jacket platform is the most widely used offshore platform. Steel rubber vibration isolator and damping isolation system are often used to reduce or isolate the ice-induced and seismic-induced vibrations. The previous experimental and theoretical studies concern mostly with dynamic properties, vibration isolation schemes and vibration-reduction effectiveness analysis. In this paper, the experiments on steel rubber vibration isolator were carried out to investigate the compressive properties and fatigue properties in different low temperature conditions. The results may provide some guidelines for design of steel rubber vibration isolator for offshore platform in a cold environment, and for maintenance and replacement of steel rubber vibration isolator, and also for fatigue life assessment of the steel rubber vibration isolator. (C) 2009 Elsevier Ltd. All rights reserved.