Achievable secrecy enchancement through joint encryption and privacy amplification

In this dissertation we try to achieve secrecy enhancement in communications by resorting to both cryptographic and information theoretic secrecy tools and metrics. Our objective is to unify tools and measures from cryptography community with techniques and metrics from information theory community that are utilized to provide privacy and confidentiality in communication systems. For this purpose we adopt encryption techniques accompanied with privacy amplification tools in order to achieve secrecy goals that are determined based on information theoretic and cryptographic metrics. Every secrecy scheme relies on a certain advantage for legitimate users over adversaries viewed as an asymmetry in the system to deliver the required security for data transmission. In all of the proposed schemes in this dissertation, we resort to either inherently existing asymmetry in the system or proactively created advantage for legitimate users over a passive eavesdropper to further enhance secrecy of the communications. This advantage is manipulated by means of privacy amplification and encryption tools to achieve secrecy goals for the system evaluated based on information theoretic and cryptographic metrics. In our first work discussed in Chapter 2 and the third work explained in Chapter 4, we rely on a proactively established advantage for legitimate users based on eavesdropper’s lack of knowledge about a shared source of data. Unlike these works that assume an errorfree physical channel, in the second work discussed in Chapter 3 correlated erasure wiretap channel model is considered. This work relies on a passive and internally existing advantage for legitimate users that is built upon statistical and partial independence of eavesdropper’s channel errors from the errors in the main channel. We arrive at this secrecy advantage for legitimate users by exploitation of an authenticated but insecure feedback channel. From the perspective of the utilized tools, the first work discussed in Chapter 2 considers a specific scenario where secrecy enhancement of a particular block cipher called Data Encryption standard (DES) operating in cipher feedback mode (CFB) is studied. This secrecy enhancement is achieved by means of deliberate noise injection and wiretap channel encoding as a technique for privacy amplification against a resource constrained eavesdropper. Compared to the first work, the third work considers a more general framework in terms of both metrics and secrecy tools. This work studies secrecy enhancement of a general cipher based on universal hashing as a privacy amplification technique against an unbounded adversary. In this work, we have achieved the goal of exponential secrecy where information leakage to adversary, that is assessed in terms of mutual information as an information theoretic measure and Eve’s distinguishability as a cryptographic metric, decays at an exponential rate. In the second work generally encrypted data frames are transmitted through Automatic Repeat reQuest (ARQ) protocol to generate a common random source between legitimate users that later on is transformed into information theoretically secure keys for encryption by means of privacy amplification based on universal hashing. Towards the end, future works as an extension of the accomplished research in this dissertation are outlined. Proofs of major theorems and lemmas are presented in the Appendix

ARQ-based symmetric-key generation over correlated erasure channels

This paper focuses on the problem of sharing secret keys using Automatic Repeat reQuest (ARQ) protocol. We consider cases where forward and feedback channels are erasure channels for a legitimate receiver (Bob) and an eavesdropper (Eve). In prior works, the wiretap channel is modeled as statistically independent packet erasure channels for Bob and Eve. In this paper, we go beyond the state-of-the-art by addressing correlated erasure events across the wiretap channel. The created randomness is shared between two legitimate parties through ARQ transmissions that is mapped into a destination set using a first-order digital filter with feedback. Then, we characterize Eve\u27s information loss about this shared destination set, due to inevitable transmission errors. This set is then transformed into a highly secure key using privacy amplification in order to intensify and exploit Eve\u27s lack of knowledge. We adopt two criteria for analysis and design of the system: secrecy outage probability as a measure of the secrecy quality, and secret key rate as a metric for efficiency. The resulting secrecy improvement is presented as a function of the correlation coefficients and the erasure probabilities for both channels. It is shown that secrecy improvement is achievable even when Eve has a better channel than legitimate receivers, and her channel conditions are unknown to legitimate users. © 2005-2012 IEEE

IEEE Transactions Information Forensics And Security :Vol. 8, No. 7-8, July-August 2013

1. Uncoordinated Cooperative Jamming for Secret Communications / Shuangyu Luo, Jiangyuan Li, Athina P. Petropulu 2. A Novel Reversible Data Hiding Scheme Based on Two-Dimensional Difference-Histogram Modification / Xiaolong Li, et al. 3. Fully Private Noninteractive Face Verification / Juan Ramon Troncoso-Pastoriza, Daniel Gonzales-Jimenez, Fernando Perez-Gonzalez 4. Iris Biometrics: Synthesis of Degraded Ocular Images / Luis Cardoso, et al. 5. On Cooperative and Maalicious Behavior in Multirelay Fading Channels / Meng-Hsi Chen, et al. 6. Recursive Linear and Differential Cryptanalysis of Ultralightweight Authentication Protocols / Zahra Ahmadian, Mahmoud Salmasizadeh, Mohammad Reza Aref 7. ARQ-Based Symmetric-Key Generation Over Correlated Erasure Channels / Yahya Sowti Khiabani, Shuangqing Wei 8. One-Receiver Two-Eavesdropper Broadcast Channel Wth Degraded Message Sets / Sadaf Salehkalaibar, Mahtab Mirmohseni, Mohammad Reza Aref 9. An Improved Discete Fourier Transform-Based Agorithm for Electric Network Frequency Extraction / Ling Fu, et al. 10. Exposing Digital Image Forgeries by Illumination Color Classification / Tiago Jose de Carvalho, et al. etc