Full name: Alexander Fok Department: Electric and Computer Engineering Supervisors: Prof. Shlomi Dolev and Prof. Michael Segal Degree: Doctor of Philosophy (Ph.D.)

:Seminar Topic Privacy Preserving Event Detection from Visual Secret Sharing to Quantum Protocols :Seminar Abstract Collaborative image matching allows a group of devices to compare an observed image with a protected reference image without giving every participant the complete reference. Such systems must also cope with participants that submit incorrect or malicious information. This seminar presents my doctoral research on this problem, from visual secret sharing to quantum protocols. I first describe distributed matching based on visual secret sharing, then show how optical wave interference supports accurate image reconstruction in the presence of Byzantine participants, under explicit threshold and system assumptions. These published results provide the foundation for discussing privacy, reconstruction quality, and resilience. I then introduce ongoing work on quantum visual encryption, where image bits are encoded as qubits in secret bases and separate participants carry out encoding, comparison, and decoding. I discuss simulation results and the security questions raised by operations on protected data. The final part considers quantum key refresh and how encoding geometry affects an eavesdropper’s information. I present a recent single-qubit comparison with ideal verification, assuming that no adversarial quantum memory survives until later compromise of the encoding key. I outline the remaining steps toward authenticated block protocols. The talk introduces the necessary quantum concepts and is intended for an audience with a general background in computer science or engineering