Survivability Considerations in Wireless Networks
Survivability is usually defined as the capability of a network to deliver data successfully in a timely manner, even in the presence of attacks. Security as well as reliability are included in survivability considerations. Due to the lossy and open nature of wireless links, design of solutions to make the network survive against attacks as well as wireless idiosyncrasies is difficult. In this dissertation, we approach several issues that have to be considered in order to ensure survivability in various contexts. Firstly, we need to understand the causes for why the network is failing or does not deliver data efficiently as supposed. Network forensics could help with this matter. However, provisioning forensic evidence could impact the network performance in terms of throughput and delay. Secondly, we need to make the network reliable when switching from commonly used bands to another, because conventional network protocols may be affected by the characteristics of that particular frequency. Finally, we need to make sure there is security for the communication relying on the online social networks against active seekers of information.
For the first issue, we examine the problem of monitoring packet level transmissions and provisioning forensic evidence. We provide an analytical framework that computes the likelihood that forensic evidence exists with respects to packet transmissions. We validate our analytical framework via simulations and real-world experiments on two different wireless testbeds. Then we use the analytical framework as a basis for a protocol within a forensic analyzer to determine the likelihood that nodes drop packets. Our assessments are shown to be close to the ground truth, with an average deviation of 2.3%. Furthermore, we quantify the trade-offs between provisioning forensic evidence and achieving high performance in wireless networks. We find that the performance remains unaffected up to a certain evidence availability requirement. Beyond this, the throughput could degrade and the delay could increase by as much as 30%.
Then, this dissertation presents our work in evaluating neighbor discovery in 60 GHz band. Neighbor discovery is a fundamental process in the self-configuration of ad-hoc wireless networks. However, the unique physical layer characteristics of 60 GHz make neighbor discovery different from that in traditional 2.4 and 5 GHz bands. In particular, neighbors can be discovered via both direct and reflected beams. We analyze two neighbor discovery approaches in 60 GHz band. We examine the impact of system parameters on the discovery efficiency.
Finally, this dissertation includes our efforts in doing covert communication on public photo-sharing sites. Steganography can be used to embed secret messages in shared images. However, the image processing performed by photo sharing sites may destroy the embedded messages. We provide an in-depth measurement study of the feasibility of hiding data on four popular photo sharing sites and identify the challenges in communicating covertly on these sites. We propose an approach of embedding secret messages while ensuring their integrity is preserved. We also present an approach for bootstrapping the communication without an out-of-band channel.