Keynotes
Keynote speakers for ProvSec 2026: To be confirmed.
Prof. Kazue Sako
Waseda University, Japan
Dr. Kazue Sako is a professor in the Department of Computer Science and Engineering at Waseda University. Her research focuses on cryptographic protocols designed to enhance privacy and fairness, including electronic voting systems, anonymous authentication schemes, and digital lottery systems. Before transitioning to academia, she worked in the industry, where she contributed to securing systems widely used in society. She currently serves on various governmental committees in Japan, including those of the Digital Agency, the Financial Services Agency, Cabinet Secretariat, the Ministry of Health, Labour, and Welfare, and the Supreme Court. Additionally, she has held roles as Program Co-Chair or Chair for numerous international conferences including ASIACRYPT, RSA conference Cryptographer's Track, Financial Cryptography and Data Security, ESORICS and PKC. She is a council member of the Science Council of Japan, and was the 26th president of Japan Society for Industrial and Applied Mathematics. She is currently serving as a vice chair of MyDataJapan.
Abstract: In today's world, where so many social activities occur online, proving one's identity has become a critical step in initiating interactions. Traditionally, this has been done using IDs and passwords, with the latter needing to be unique and sufficiently complex for each service. However, with the advent of digital signatures and zero-knowledge proofs, a more secure and privacy-preserving approach is possible: using a pair of public and secret keys as a universal ID and password across multiple services and incorporate unlinkable selective disclosure and predicate proofs, to enhance privacy.
In this talk, we will explore some of the challenges involved in bringing these advancements into practical use within our society. One key example is the framework of Verifiable Credentials, which allows individuals to assert their identity or specific attributes necessary to access services. It is crucial to reexamine what properties need to be proven in realistic scenarios to ensure these systems are both effective and aligned with real-world environments.
Prof. Man Ho (Allen) Au
The Hong Kong Polytechnic University, Hong Kong
Prof. Man Ho Allen Au is a Full Professor at the Department of Computing of The Hong Kong Polytechnic University. His research interests include information security, cryptography, blockchain technology, and their applications. He has published over 200 refereed papers in top journals and conferences, including CRYPTO, ASIACRYPT, ACM CCS, NDSS, IEEE S&P, SIGMOD, SOSP, IEEE TIFS, IEEE TDSC, and others. He was a recipient of the 2023 BOCHK Science and Technology Innovation Prize (STIP) in FinTech and 2009 PET runner-up award for outstanding research in privacy-enhancing technologies. His team won the ZPrize - Open Division Plonk-DIZK GPU Acceleration prize, which came with a cash award of 550K USD. He has been ranked as HKU Scholar in the Top 1% (by Clarivate Analytics in the top 1% worldwide by citations) in 2020 - 2022. He is also listed as the World's Top 2% Scientists by single-year impact and by career-long impact in the list published by Stanford University in Oct 2022 and Oct 2023.
Abstract: Due to its additive homomorphism, the Paillier cryptosystem is renowned for its applications in electronic voting, threshold signatures, verifiably encrypted signatures, privacy-preserving data analytics, secure multi-party computation, and more. In these applications, it is necessary to conduct zero-knowledge proof of correct encryption and/or range proof to maintain security against active attacks. .
In this talk, we will discuss some of the applications of the Paillier cryptosystem, highlighting why zero-knowledge proofs are necessary. Then, we will present our recent results. The first result is a general zero-knowledge argument system customized for the Paillier cryptosystem. It is useful when the number of Paillier ciphertext is large. Our system enjoys sublinear (amortised) proof size, low verification cost, and acceptable proof generation cost. It can be used to prove typical relations in Paillier cryptosystems including range proof, correctness proof, relationships between bits of plaintext, relationships of plaintexts among multiple ciphertexts, and more. Our second result is a direct range proofs for the Paillier cryptosystem, specifically aimed at optimizing those for both Paillier plaintext and affine operation. Finally, we showed how our proof system can be used to improve existing schemes utilizing range proof for Paillier cryptosystems.