Building Security Protocols Against Powerful Adversaries

As our sensitive data is increasingly carried over the Internet and stored remotely, security in communications becomes a fundamental requirement. Yet, today's security practices are designed around assumptions the validity of which is being challenged. In this thesis we design new security mechanisms for certain scenarios where traditional security assumptions do not hold. First, we design secret-agreement protocols for wireless networks, where the security of the secrets does not depend on assumptions about the computational limitations of adversaries. Our protocols leverage intrinsic characteristics of the wireless to enable nodes to agree on common pairwise secrets that are secure against computationally unconstrained adversaries. Through testbed and simulation experimentation, we show that it is feasible in practice to create thousands of secret bits per second. Second, we propose a traffic anonymization scheme for wireless networks. Our protocol aims in providing anonymity in a fashion similar to Tor - yet being resilient to computationally unbounded adversaries - by exploiting the security properties of our secret-agreement. Our analysis and simulation results indicate that our scheme can offer a level of anonymity comparable to the level of anonymity that Tor does. Third, we design a lightweight data encryption protocol for protecting against computationally powerful adversaries in wireless sensor networks. Our protocol aims in increasing the inherent weak security that network coding naturally offers, at a low extra overhead. Our extensive simulation results demonstrate the additional security benefits of our approach. Finally, we present a steganographic mechanism for secret message exchange over untrustworthy messaging service providers. Our scheme masks secret messages into innocuous texts, aiming in hiding the fact that secret message exchange is taking place. Our results indicate that our schemes succeeds in communicating hidden information at non-negligible rates

PRMP : a scaleable polling-based reliable multicast protocol

PhD ThesisTraditional reliable unicast protocols (e.g., TCP), known as sender-initiated schemes, do not scale well for one-to-many reliable multicast due mainly to implosion losses caused by excessive rate of feedback packets arriving from receivers. So, recent multicast protocols have been devised following the receiver- initiated approach: scalability (in terms of control traffic, protocol state and end-systems processing requirements) is achieved by making the sender independent from receivers; the sender does not know the membership of the destination group. However, this comes with a cost: the lack of knowledge about and control of receivers at the sender has negative implications with respect to throughput, network cost (bandwidth required), and degree of reliability offered to applications. This thesis follows an alternative approach: instead of adopting the receiver-initiated scheme, it greatly enhances the scalability of the sender-initiated scheme, by means of polling-based feedback and hierarchy. The resulting protocol is named PRMP: polling-based Reliable Multicast protocol. Its unique implosion avoidance mechanism polls receivers at carefully planned timing instants achieving a low and uniformly distributed rate of feedback packets. The sender retains controls of receivers: the main PRMP mechanisms are based on a one-to-many sliding window mechanism, which efficiently and elegantly extends the abstraction from reliable unicasting to reliable multicasting. The error control mechanism of PRMP incorporates the use of NACKs and selective, cumulative acknowledgment of packets; additionally, it can wait and judiciously decide between multicast and selective unicast retransmissions. The flow control mechanism prevents unnecessary losses caused by the overrunning of receivers, despite variations in round-trip times and application speeds. The scalability provided by the polling mechanism is further extended by an hierarchic organization to exploit distributed processing and local recovery: receivers are organized according to a tree-structure. However, unlike other tree-based protocols, PRMP is "fully-hierarchic": each parent node forwards data via multicast to its children, and retains/explores the control of and knowledge about its children while autonomously applying error, flow, congestion and session controls in the communication with them. Two congestion control mechanisms, one window-based and another rate-based, have been incorporated to PRMP. As shown through simulation experiments, the resulting protocol q,chieves high though put with cost- effective reliable multicasting. They also show the scalability and effectiveness of PRMP mechanisms. PRMP can achieve reliable multicast with the same kind of reliability guarantees provided by TCP but without incurring prohibitive costs in terms of network cost or recovery latency found in other protocols.Brazilian Research Agency CAPE

Hardware Support for Efficient Packet Processing

Scalability is the key ingredient to further increase the performance of today’s supercomputers. As other approaches like frequency scaling reach their limits, parallelization is the only feasible way to further improve the performance. The time required for communication needs to be kept as small as possible to increase the scalability, in order to be able to further parallelize such systems. In the first part of this thesis ways to reduce the inflicted latency in packet based interconnection networks are analyzed and several new architectural solutions are proposed to solve these issues. These solutions have been tested and proven in a field programmable gate array (FPGA) environment. In addition, a hardware (HW) structure is presented that enables low latency packet processing for financial markets. The second part and the main contribution of this thesis is the newly designed crossbar architecture. It introduces a novel way to integrate the ability to multicast in a crossbar design. Furthermore, an efficient implementation of adaptive routing to reduce the congestion vulnerability in packet based interconnection networks is shown. The low latency of the design is demonstrated through simulation and its scalability is proven with synthesis results. The third part concentrates on the improvements and modifications made to EXTOLL, a high performance interconnection network specifically designed for low latency and high throughput applications. Contributions are modules enabling an efficient integration of multiple host interfaces as well as the integration of the on-chip interconnect. Additionally, some of the already existing functionality has been revised and improved to reach better performance and a lower latency. Micro-benchmark results are presented to underline the contribution of the made modifications

Formal modelling and analysis of denial of services attacks in wireless sensor networks

Wireless Sensor Networks (WSNs) have attracted considerable research attention in recent years because of the perceived potential benefits offered by self-organising, multi-hop networks consisting of low-cost and small wireless devices for monitoring or control applications in di±cult environments. WSN may be deployed in hostile or inaccessible environments and are often unattended. These conditions present many challenges in ensuring that WSNs work effectively and survive long enough to fulfil their functionalities. Securing a WSN against any malicious attack is a particular challenge. Due to the limited resources of nodes, traditional routing protocols are not appropriate in WSNs and innovative methods are used to route data from source nodes to sink nodes (base stations). To evaluate the routing protocols against DoS attacks, an innovative design method of combining formal modelling and computer simulations has been proposed. This research has shown that by using formal modelling hidden bugs (e.g. vulnerability to attacks) in routing protocols can be detected automatically. In addition, through a rigorous testing, a new routing protocol, RAEED (Robust formally Analysed protocol for wirEless sEnsor networks Deployment), was developed which is able to operate effectively in the presence of hello flood, rushing, wormhole, black hole, gray hole, sink hole, INA and jamming attacks. It has been proved formally and using computer simulation that the RAEED can pacify these DoS attacks. A second contribution of this thesis relates to the development of a framework to check the vulnerability of different routing protocols against Denial of Service(DoS) attacks. This has allowed us to evaluate formally some existing and known routing protocols against various DoS attacks iand these include TinyOS Beaconing, Authentic TinyOS using uTesla, Rumour Routing, LEACH, Direct Diffusion, INSENS, ARRIVE and ARAN protocols. This has resulted in the development of an innovative and simple defence technique with no additional hardware cost for deployment against wormhole and INA attacks. In the thesis, the detection of weaknesses in INSENS, Arrive and ARAN protocols was also addressed formally. Finally, an e±cient design methodology using a combination of formal modelling and simulation is propose to evaluate the performances of routing protocols against DoS attacks

Measurement-Driven Algorithm and System Design for Wireless and Datacenter Networks

The growing number of mobile devices and data-intensive applications pose unique challenges for wireless access networks as well as datacenter networks that enable modern cloud-based services. With the enormous increase in volume and complexity of traffic from applications such as video streaming and cloud computing, the interconnection networks have become a major performance bottleneck. In this thesis, we study algorithms and architectures spanning several layers of the networking protocol stack that enable and accelerate novel applications and that are easily deployable and scalable. The design of these algorithms and architectures is motivated by measurements and observations in real world or experimental testbeds. In the first part of this thesis, we address the challenge of wireless content delivery in crowded areas. We present the AMuSe system, whose objective is to enable scalable and adaptive WiFi multicast. AMuSe is based on accurate receiver feedback and incurs a small control overhead. This feedback information can be used by the multicast sender to optimize multicast service quality, e.g., by dynamically adjusting transmission bitrate. Specifically, we develop an algorithm for dynamic selection of a subset of the multicast receivers as feedback nodes which periodically send information about the channel quality to the multicast sender. Further, we describe the Multicast Dynamic Rate Adaptation (MuDRA) algorithm that utilizes AMuSe's feedback to optimally tune the physical layer multicast rate. MuDRA balances fast adaptation to channel conditions and stability, which is essential for multimedia applications. We implemented the AMuSe system on the ORBIT testbed and evaluated its performance in large groups with approximately 200 WiFi nodes. Our extensive experiments demonstrate that AMuSe can provide accurate feedback in a dense multicast environment. It outperforms several alternatives even in the case of external interference and changing network conditions. Further, our experimental evaluation of MuDRA on the ORBIT testbed shows that MuDRA outperforms other schemes and supports high throughput multicast flows to hundreds of nodes while meeting quality requirements. As an example application, MuDRA can support multiple high quality video streams, where 90% of the nodes report excellent or very good video quality. Next, we specifically focus on ensuring high Quality of Experience (QoE) for video streaming over WiFi multicast. We formulate the problem of joint adaptation of multicast transmission rate and video rate for ensuring high video QoE as a utility maximization problem and propose an online control algorithm called DYVR which is based on Lyapunov optimization techniques. We evaluated the performance of DYVR through analysis, simulations, and experiments using a testbed composed of Android devices and o the shelf APs. Our evaluation shows that DYVR can ensure high video rates while guaranteeing a low but acceptable number of segment losses, buffer underflows, and video rate switches. We leverage the lessons learnt from AMuSe for WiFi to address the performance issues with LTE evolved Multimedia Broadcast/Multicast Service (eMBMS). We present the Dynamic Monitoring (DyMo) system which provides low-overhead and real-time feedback about eMBMS performance. DyMo employs eMBMS for broadcasting instructions which indicate the reporting rates as a function of the observed Quality of Service (QoS) for each UE. This simple feedback mechanism collects very limited QoS reports which can be used for network optimization. We evaluated the performance of DyMo analytically and via simulations. DyMo infers the optimal eMBMS settings with extremely low overhead, while meeting strict QoS requirements under different UE mobility patterns and presence of network component failures. In the second part of the thesis, we study datacenter networks which are key enablers of the end-user applications such as video streaming and storage. Datacenter applications such as distributed file systems, one-to-many virtual machine migrations, and large-scale data processing involve bulk multicast flows. We propose a hardware and software system for enabling physical layer optical multicast in datacenter networks using passive optical splitters. We built a prototype and developed a simulation environment to evaluate the performance of the system for bulk multicasting. Our evaluation shows that the optical multicast architecture can achieve higher throughput and lower latency than IP multicast and peer-to-peer multicast schemes with lower switching energy consumption. Finally, we study the problem of congestion control in datacenter networks. Quantized Congestion Control (QCN), a switch-supported standard, utilizes direct multi-bit feedback from the network for hardware rate limiting. Although QCN has been shown to be fast-reacting and effective, being a Layer-2 technology limits its adoption in IP-routed Layer 3 datacenters. We address several design challenges to overcome QCN feedback's Layer- 2 limitation and use it to design window-based congestion control (QCN-CC) and load balancing (QCN-LB) schemes. Our extensive simulations, based on real world workloads, demonstrate the advantages of explicit, multi-bit congestion feedback, especially in a typical environment where intra-datacenter traffic with short Round Trip Times (RTT: tens of s) run in conjunction with web-facing traffic with long RTTs (tens of milliseconds)