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Topic

Privacy-Preserving Protocols: Advancing Security and Flexibility with Policy-Based Sanitizable Signatures and Fair Exchange Mechanisms

Department of Electrical and Computer Engineering

Date & location

• Wednesday, April 23, 2025

• 10:00 A.M.

• Virtual Defence

Reviewers

Supervisory Committee

• Dr. Riham AlTawy, Department of Electrical and Computer Engineering, University of Victoria(Co-Supervisor)

• Dr. Issa Traore, Department of Electrical and Computer Engineering, UVic (Member)

• Dr. Yun Lu, Department of Computer Science, UVic (Outside Member) 

External Examiner

• Dr. Huapeng Wu, Department of Electrical and Computer Engineering, University of Windsor 

Chair of Oral Examination

• Dr. Jianping Pan, Department of Computer Science, UVic 

Abstract

This dissertation presents advancements in privacy-preserving protocols, focusing on two research areas: policy-based sanitizable signature schemes and fair exchange mechanisms.

Sanitizable signature schemes allow designated parties to modify or sanitize signed messages while preserving the message’s authenticity. We present the Unlinkable Policy-Based Sanitizable Signature (UP3S) scheme, which addresses a significant deficiency in existing policy-based sanitizable signature schemes, the lack of unlinkability. A crucial security property, particularly in privacy-sensitive applications, unlinkability guarantees that distinct sanitized versions of a given message cannot be linked to the original message or to each other, even across multiple sanitization operations.

Building upon UP3S, we investigate extending its capabilities to support fine-grained control over message modifications. This involves enabling multiple modification policies for a single message and facilitating the delegation of sanitization rights. To this end, we propose the Traceable Policy-Based Signature (TPBS) scheme, which forms the basis for the Extended Policy-Based Sanitizable Signature (EP3S). EP3S offers a flexible and se cure framework for policy-based Sanitizable signatures, incorporating enhanced control over message modifications and sanitization-rights delegation. In the area of fair exchange mechanisms, our contributions focus on privacy-preserving exchanges of both digital and physical assets. We introduce V2VFx, a privacy-preserving framework for the fair exchange of physical assets, specifically in vehicle-to-vehicle energy trading. Together, these contributions advance the state of privacy-preserving protocols by ad dressing key limitations in existing schemes and extending their applicability.