Security by typing

We present an approach for analyzing cryptographic protocols that are subject to attack from an active intruder who takes advantage of knowledge of the protocol rules. The approach uses a form of type system in which types are communication steps and typing constraints characterize all the messages available to the intruder. This reduces verification of authentication and secrecy properties to a typing problem in our type system. We present the typing rules, prove soundness of a type inference algorithm, and establish the correctness of the typing rules with respect to the protocol execution and intruder actions. The protocol specifications used in the approach can be automatically extracted from the conventional, informal cryptographic protocol notation commonly found in the literature. To validate the approach, we implement our algorithm in a tool called DYMNA, which is a practical and efficient environment for the specification and analysis of cryptographic protocols.     

SPA:新的高效安全协议分析系统

研制高效的自动分析系统是密码协议安全性分析的一项关键任务,然而由于密码协议的分析非常复杂,存在大量未解决的问题,使得很多现有分析系统在可靠性和效率方面仍存在许多局限性．该文基于一种新提出的密码协议代数模型和安全性分析技术,设计并实现了一个高效的安全协议安全性自动分析系统(Security Protocol Analyzer,SPA)．首先对协议安全目标进行规范,然后从初始状态出发,采用有效的搜索算法进行分析证明,试图发现针对协议的安全漏洞．使用该系统分析了10多个密码协议的安全性,发现了一个未见公开的密码协议攻击实例．实验数据显示,该系统与现有分析工具相比,具有较高的分析可靠性和效率,可作为网络系统安全性评测以及密码协议设计的有效辅助工具．     

Reducing Protocol Analysis with XOR to the XOR-Free Case in the Horn Theory Based Approach

In the Horn theory based approach for cryptographic protocol analysis, cryptographic protocols and (Dolev?CYao) intruders are modeled by Horn theories and security analysis boils down to solving the derivation problem for Horn theories. This approach and the tools based on this approach, including ProVerif, have been very successful in the automatic analysis of cryptographic protocols. However, dealing with the algebraic properties of operators, such as the exclusive OR (XOR), which are frequently used in cryptographic protocols has been problematic. In particular, ProVerif cannot deal with XOR. In this paper, we show how to reduce the derivation problem for Horn theories with XOR to the XOR-free case. Our reduction works for an expressive class of Horn theories. A large class of intruder capabilities and protocols that employ the XOR operator can be modeled by these theories. Our reduction allows us to carry out protocol analysis using tools, such as ProVerif, that cannot deal with XOR, but are very efficient in the XOR-free case. We implemented our reduction and, in combination with ProVerif, used it for the fully automatic analysis of several protocols that employ the XOR operator. Among others, our analysis revealed a new attack on an IBM security module.     

Algebra model and security analysis for cryptographic protocols

With the rapid growth of the Internet and the World Wide Web a large number of cryptographic protocols have been deployed in distributed systems for various application requirements, and security problems of distributed systems have become very important issues. There are some natural problems: does the protocol have the right properties as dictated by the requirements of the system? Is it still secure that multiple secure cryptographic protocols are concurrently executed? How shall we analy…     

基于串空间的Athena分析技术研究

基于串空间模型的研究是当前安全协议领域的一个研究热点。Song对串空间模型进行了扩展,将模型检验和定理证明结合起来,提出了一种取名为Athena的安全协议分析方法,并基于该方法开发了自动证明工具APV,Song的工作被认为是串空间理论发展的一个重要事件。本文对Athena进行了系统的分析,介绍了Athena的假设条件,给出了Athena的语法和语义,分析了该逻辑的优点和局限性,在此基础上,分析了Athena的核心算法,讨论了Athena算法自动高效的原因,以及该算法如何避免状态空间爆炸的技术,指出了该算法的缺陷,形成原因以及解决的一般方法。最后对Athena方法的发展方向进行了讨论。     

一种基于问题求解理论的密码协议形式模型

提出了一种基于问题求解理论的密码协议模型，给出了模型的基本语法以及基于ρ演算的形式语义，明确了模型推理过程中涉及到的一些关键性的概念和命题。该模型具有以下特点：能够对密码协议进行精确的形式化描述；具有合理可靠的可证明语义；对密码协议安全性的定义精确合理；便于实现自动化推理。所有这些均确保了基于该模型的密码协议安全性分析的合理性和有效性，为正确的分析密码协议的安全性提供了可靠依据。     

Using Forward Reachability Analysis for Verification of Lossy Channel Systems

We consider symbolic on-the-fly verification methods for systems of finite-state machines that communicate by exchanging messages via unbounded and lossy FIFO queues. We propose a novel representation formalism, called simple regular expressions (SREs), for representing sets of states of protocols with lossy FIFO channels. We show that the class of languages representable by SREs is exactly the class of downward closed languages that arise in the analysis of such protocols. We give methods for computing (i) inclusion between SREs, (ii) an SRE representing the set of states reachable by executing a single transition in a system, and (iii) an SRE representing the set of states reachable by an arbitrary number of executions of a control loop. All these operations are rather simple and can be carried out in polynomial time.With these techniques, one can straightforwardly construct an algorithm which explores the set of reachable states of a protocol, in order to check various safety properties. We also show how one can perform model-checking of LTL properties, using a standard automata-theoretic construction. It should be noted that all these methods are by necessity incomplete, even for the class of protocols with lossy channels.To illustrate the applicability of our methods, we have developed a tool prototype and used the tool for automatic verification of (a parameterized version of) the Bounded Retransmission Protocol.     

Tools for cryptographic protocols analysis: A technical and experimental comparison

The tools for cryptographic protocols analysis based on state exploration are designed to be completely automatic and should carry out their job with a reasonable amount of computing and storage resources, even when run by users having a limited amount of expertise in the field. This paper compares four tools of this kind to highlight their features and ability to detect bugs under the same experimental conditions. To this purpose, the ability of each tool to detect known flaws in a uniform set of well-known cryptographic protocols has been checked. Results are also given on the relative performance of the tools when analysing several known-good protocols with an increasing number of parallel sessions.     

BOMM 算法的密码学性质

BOMM(byte-oriented memorial mixer)算法是一种基于字节操作的混合型带记忆的序列扰乱算法,因具备良好的密码学性质,一个新的流密码算法Loiss使用了它作为主要组件.建立了BOMM算法的5次代数方程系统,在此基础上讨论了针对Loiss算法的代数攻击的复杂度.此外还发现了BOMM算法的一个统计弱点,并分析了Loiss算法在一类弱密钥下的安全性.     

一种新的安全协议验证方法

提出了一种基于Petri网的安全协议形式化描述和安全性验证的方法．该方法的特点是利用逆向状态分析和Petri网的状态可达性分析，判定协议运行过程中可能出现的不安全状态以及这些状态是否可达．通过实例证明了这种方法的有效性．     

Formal analysis of some secure procedures for certificate delivery

This paper describes and formally analyses two communication protocols that manage the secure emission of digital certificates. The formal analysis is carried out by means of a software tool for the automatic verification of cryptographic protocols with finite behaviour. The tool is able to discover, at a conceptual level, attacks against security procedures. The methodology is general enough to be applied to several kinds of cryptographic procedures and protocols. It is the opinion of the authors that this approach contributes towards a better understanding of the structure and aims of a protocol, for developers, analysers and final users. Copyright © 2005 John Wiley & Sons, Ltd.     

Improving the security of industrial networks by means of formal verification

Computer networks are exposed to serious security threats that can even have catastrophic consequences from both the points of view of economy and safety if such networks control critical infrastructures, such as for example industrial plants. Security must then be considered as a fundamental issue starting from the earlier phases of the design of a system, and suitable techniques and tools should be adopted to satisfy the security-related requirements. The focus of this paper is on how formal methods can help in analysing the standard cryptographic protocols used to implement security-critical services such as authentication and secret keys distribution in critical environments. The analysis of the 802.11 shared key authentication protocol by S³A, a fully automatic software tool that is based on a formal approach, is illustrated as a case study, which also highlights the peculiarities of analysing protocols based on wireless channels.     

Neuman-Stubblebine协议的串空间模型及分析

串空间模型是一种新兴的密码协议形式化分析工具,其理论中理想和诚实概念的提出大大减少了协议的证明步骤.首次利用串空间理论从机密性和认证性两个方面对Neuman-Stubblebine协议进行了分析.分析结果证明该协议是安全的,而且理想对公开密钥算法和对称密钥算法产生的协议的分析都是有效的.     

代数次数的求解算法及其在SIMON-like算法中的应用

代数次数作为布尔函数重要的密码学指标,在密码算法的设计与分析中有着重要的应用.主要研究布尔函数代数次数的求解及其在分组密码SIMON-like算法中的应用.首先,在利用真值表求解代数正规型算法的基础上建立了基于CUDA的并行求解架构,协同利用CPU和GPU的计算资源,极大地缩短了求解代数次数的时间,在较短的时间内求解了SIMON32算法和SIMECK32算法任意轮数的代数正规型和代数次数;其次,在Cube攻击理论的基础上,根据代数次数和超多项式取值之间的关系,设计了估计代数次数的概率算法,估计了一般SIMON-like算法布尔函数的代数次数;最后,从布尔函数代数次数的角度出发,给出了SIMON-like算法在选择不同循环移位参数表现的差异性,进而给出循环移位参数的选取依据.实验结果表明,SIMON算法在原始参数下,达到最大代数次数所需的轮数最短,原始参数具有更高的安全性.     

一种并发程序依赖性分析方法

并发程序的依赖性分析是并发程序分析，理解，调试，测试和维护的重要手段，由于并发程序执行的不确定性，目前，尚有很多难点有待解决，针对Ada任务机制，首先提出了一种简洁，有效的并发程序表示方法－并发程序流图，然后讨论了由任务间同步引起的同步依赖和由访问共享变量引起的任务数据依赖，建立了并发程序依赖图，并在此基础上给出了一种有效的并发程序依赖性分析算法，得到一个比较精确的依赖性，较好地解决了并发程序依赖关系不可传递性问题。     

群组密钥协商协议的安全性分析方法研究

群组密钥协商允许多个用户通过不安全的信道建立一个共享的会话密钥,设计安全的群组密钥协商协议是最基本的密码学任务之一。介绍了群组密钥协商协议的两类安全性分析方法:计算复杂性方法和形式化分析方法,详细讨论了计算复杂性方法中的关键技术,包括基于规约的证明技术及基于模拟的证明技术、基于规约的安全模型和基于模拟的安全模型,探讨了安全性分析方法的发展趋势。     

算法演化的形式归约及其性质

使用归纳过程说明算法的演化,建立了一阶语言语句集和算法的关系,并提出了启发式的归纳规则.还提出了算法分析的概率式研究方法.这种方法为有效算法的设计和自动算法设计提供了工具.     

加密模式与密码协议的安全性

密码协议的设计和安全性分析是困难的,在密码协议中总是以所使用的密码算法是安全的为前提,但是人们却忽略了密码算法的加密模式对密码协议安全性的影响。论文针对一个改进的Needham-Schroeder协议,假设其使用了分组密码的CBC加密模式,我们通过使用一条旧信息的明密文对来修改当前会话中的信息,从而成功地欺骗用户双方,并分别与他们建立了一个会话密钥,对该协议进行了成功的攻击。结果说明密码算法的加密模式对密码协议的安全性有着巨大的影响。Schroederauthenticationprotocol125     

基于逻辑编程的EKE协议分析

基于逻辑编程规则及Spi演算提出了一种验证密码协议安全性的新方法,利用该方法可以对密码协议的安全性质以程序化的方式进行验证。通过对EKE协议进行的分析,不但证明了协议已知的漏洞,而且发现了针对EKE协议的一个新的攻击——并行会话攻击。很好地验证了该新方法对密码协议的分析能力。