Securing Multi-Layer Communications: A Signal Processing Approach

Security is becoming a major concern in this information era. The development in wireless communications, networking technology, personal computing devices, and software engineering has led to numerous emerging applications whose security requirements are beyond the framework of conventional cryptography. The primary motivation of this dissertation research is to develop new approaches to the security problems in secure communication systems, without unduly increasing the complexity and cost of the entire system. Signal processing techniques have been widely applied in communication systems. In this dissertation, we investigate the potential, the mechanism, and the performance of incorporating signal processing techniques into various layers along the chain of secure information processing. For example, for application-layer data confidentiality, we have proposed atomic encryption operations for multimedia data that can preserve standard compliance and are friendly to communications and delegate processing. For multimedia authentication, we have discovered the potential key disclosure problem for popular image hashing schemes, and proposed mitigation solutions. In physical-layer wireless communications, we have discovered the threat of signal garbling attack from compromised relay nodes in the emerging cooperative communication paradigm, and proposed a countermeasure to trace and pinpoint the adversarial relay. For the design and deployment of secure sensor communications, we have proposed two sensor location adjustment algorithms for mobility-assisted sensor deployment that can jointly optimize sensing coverage and secure communication connectivity. Furthermore, for general scenarios of group key management, we have proposed a time-efficient key management scheme that can improve the scalability of contributory key management from O(log n) to O(log(log n)) using scheduling and optimization techniques. This dissertation demonstrates that signal processing techniques, along with optimization, scheduling, and beneficial techniques from other related fields of study, can be successfully integrated into security solutions in practical communication systems. The fusion of different technical disciplines can take place at every layer of a secure communication system to strengthen communication security and improve performance-security tradeoff

Coordinated Sensor Deployment for Improving Secure Communications and Sensing Coverage

Sensor network has a great potential in applications such as habitat monitoring, wildlife tracking, building surveillance, and military combat. The design of a sensor network system involves several important issues, including the sensing coverage, node-to-node or node-to-base-station communications, and the security in information gathering and relay by the sensors. In this paper, we show that the system performance on these aspects depends closely on how the sensors are deployed in the field, and on how the sensor locations can be adjusted after the initial deployment. For static sensor deployment, we investigate the hexagon and square lattice topology and analyze their impact on secure connectivity and sensing coverage. For advanced sensing devices that allow for location adjustment after deployment, we have established a new framework for coordinated updates of sensor locations. We propose two new sensor location updating algorithms, the VFSec and the Weighted Centroid algorithm, to jointly optimize sensing coverage and secure connectivity. Simulation results show that these new algorithms provide superior tradeoff over the existing approaches that do not take security into considerations

COLLUSION-RESISTANT INTENTIONAL DE-SYNCHRONIZATION FOR DIGITAL VIDEO FINGERPRINTING

A powerful class of attacks in multimedia fingerprinting is known as collusion attacks, where a clique of colluders, each having a copy of the same multimedia content with different fingerprint, combine their copies to form a colluded copy. In this paper, we propose a countermeasure against collusion attacks for digital video: pseudo-random intentional de-synchronization techniques. Each user’s copy of video is slightly pseudo-randomly changed (desynchronized) in such a way that these changes will not be noticeable for an individual copy, but will be significant enough to produce perceptual artifacts when multiple copies are combined (e.g., via averaging, replacement attacks, etc.). To achieve this task, we propose several novel effective techniques, including constrained random temporal and spatial sampling. We discuss feasibility issues and limitations of video de-synchronization, and present several examples. 1