Randomized gossip algorithms under attack

Recently, gossip-based algorithms have received significant attention for data aggregation in distributed environments. The main advantage of gossip-based algorithms is their robustness in dynamic and fault-prone environments with unintentional faults such as link failure and channel noise. However, the robustness of such algorithms in hostile environments with intentional faults has remained unexplored. In this paper, we call attention to the risks which may be caused by the use of gossip algorithms in hostile environments, i.e., when some malicious nodes collude to skew aggregation results by violating the normal execution of the protocol. We first introduce a model of hostile environment and then examine the behavior of randomized gossip algorithms in this model using probabilistic analysis. Our model of hostile environment is general enough to cover a wide range of attacks. However, to achieve stronger results, we focus our analysis on fully connected networks and some powerful attacks. Our analysis shows that in the presence of malicious nodes, after some initial steps, randomized gossip algorithms reach a point at which the lengthening of gossiping is harmful, i.e., the average accuracy of the estimates of the aggregate value begins to decrease strictly.     

Onion under Microscope: An in-depth analysis of the Tor Web

World Wide Web - Tor is an open source software that allows accessing various kinds of resources, known as hidden services, while guaranteeing sender and receiver anonymity. Tor relies on a free,...     

Risk-based attack strategies for mobile ad hoc networks under probabilistic attack modeling framework

In this paper, we introduce and design a modeling framework that allows for the study and analysis of attack propagation in mobile ad hoc networks. The choice of a statistical approach for the problem is motivated by the dynamic characteristics of the ad hoc topology and the stochastic nature of threat propagation. Based on this probabilistic modeling framework, we study the impact of topology and mobility in the propagation of software threats over ad hoc networks. We design topology control algorithms that indicate how to properly adjust an attacker’s transmission radius, according to the measured topological characteristics and availability of its resources, in the process of infecting a network more effectively. Then based on these topology control algorithms we develop different attack strategies that may range from independent attacks to cooperative scenarios in order to increase the negative impact of an attack on the network. Our performance evaluation results demonstrate that the proposed topology control algorithms and respective attack strategies effectively balance the tradeoffs between the potential network damage and the attackers’ lifetime, and as a result significantly outperform any other flat and threshold-based approaches.     

Tor隐匿服务可扩展性研究

随着网络服务的发展与人们对隐私要求的日益提高。在提供用户通信匿名的基础上,产生了保护服务器匿名性的需求。第二代洋葱路由The Second Generation Onion Router(Tor)的隐匿服务功能就完美地实现了这样的需求。然而自其提出至今已逾10年,其隐匿服务技术并未得到良好的发展。近年来,随着网络服务规模的不断扩大,在Tor网络上架设大型网络服务,或将网络服务迁移至Tor网络中的需求逐渐增多。然而,在隐匿服务设计之初,由于其实现只考虑了单核单线程的情况,并未能充分利用现在流行的多核架构,也不支持负载均衡等技术。因而,其可扩展性成为了服务提供者需要解决的首要问题。本文通过使用相同的主机名与私钥运行多个隐匿服务实例来解决其可扩展性问题,并使用Shadow在离线环境下进行仿真,最终通过实验分析了这种方式对Tor隐匿服务带来的性能提升及可能存在的问题。     

Network security under siege: the timing attack

Although most encryption algorithms are theoretically secure and remain impervious to even the most sophisticated cryptanalytic techniques, new attacks like the timing attack exploit the engineering side of network security. A timing attack is basically a way of deciphering a user's private key information by measuring the time it takes to carry out cryptographic operations. Factors such as branching and conditional statements, RAM cache hits, processor instructions that run in nonfixed time, as well as performance optimizations to bypass unnecessary operations, all contribute to predictability and therefore to the probability of key decryption     

Protocol-level attacks against Tor

Tor is a real-world, circuit-based low-latency anonymous communication network, supporting TCP applications over the Internet. In this paper, we present an extensive study of protocol-level attacks against Tor. Different from existing attacks, the attacks investigated in this paper can confirm anonymous communication relationships quickly and accurately by manipulating one single cell and pose a serious threat against Tor. In these attacks, a malicious entry onion router may duplicate, modify, insert, or delete cells of a TCP stream from a sender, which can cause cell recognition errors at the exit onion router. If an accomplice of the attacker at the entry onion router also controls the exit onion router and recognizes such cell recognition errors, the communication relationship between the sender and receiver will be confirmed. These attacks can also be used for launching the denial-of-service (DoS) attack to disrupt the operation of Tor. We systematically analyze the impact of these attacks and our data indicate that these attacks may drastically degrade the anonymity service that Tor provides, if the attacker is able to control a small number of Tor routers. We have implemented these attacks on Tor and our experiments validate their feasibility and effectiveness. We also present guidelines for defending against protocol-level attacks.     

一种混合的Tor匿名通信系统

提出了一种混合的Tor匿名通信系统方案,它不仅能够保证Tor系统低的通信延迟,而且还能够排除其因未使用填充信息和批量处理技术而导致的安全问题.它确保了Tor匿名通信系统能够更加可靠地运行,实现用户身份隐藏.     

Security of autoregressive speech watermarking model under guessing attack

The security of the "autoregressive (AR) watermark in AR host" signal model is investigated. It is demonstrated through analysis and Monte Carlo simulation that the AR watermarking model is asymptotically as secure as the "white watermark in white host" model under the guessing attack.     

不同攻击模式下城市公交网络抗毁性分析

为了保证城市公交网络的安全运营、提高整个交通网络运行效率,以成都市公交网络为例,分析了该网络的拓扑结构特性,研究了该网络在随机攻击和蓄意攻击下的抗毁性。仿真结果表明,网络在随机攻击和基于节点度的攻击下连续移除节点的数目几乎不对网络的抗毁性产生影响,而在基于节点介数和效率的攻击下连续移除的节点个数越少,网络的抗毁性越差;基于节点介数的攻击对网络抗毁性产生的影响要比随机、基于节点度和效率更为显著。