Speaker Bio:

Dr. Rupeng Yang is currently a lecturer at the school of computing and information technology at University of Wollongong. Prior to joining UOW, he was a postdoc researcher at The University of Hong Kong, hosted by Prof. Man Ho Au. He received his PhD at Shandong University in 2019, advised by Prof. Qiuliang Xu. He is interested in theoretical and applied cryptography, including Lattice-Based Cryptography, Cryptographic Watermarking, Privacy-Preserving Protocols, Public Key Encryption and Foundation of Cryptography.

Date: May 14, 2025

Time: 09:00-10:30

Location: Room 320, Ganchang Court D

Abstract:

We construct fully homomorphic encryption (FHE) schemes with chosen-ciphertext (CCA) security from the learning with errors (LWE) assumption in the standard model. Security of our construction only relies on the circular-secure LWE, which matches the assumptions needed for FHE with the basic chosen-plaintext security. Besides, the scheme achieves a security notion that is strictly stronger than the CCA1 security. Prior FHE schemes with even just CCA1 security require either the random oracle model or non-falsifiable knowledge assumptions.

The construction follows the well-known Naor-Yung double encryption paradigm. However, unlike previous works [Boneh et al., ITCS 2012; Canetti et al., PKC 2017; Manulis and Nguyen, Eurocrypt 2024], which employ general zero-knowledge succinct non-interactive arguments of knowledge (ZK-SNARKs), we design a special succinct argument to prove the validity of FHE ciphertexts. The succinct argument is constructed from batch arguments for NP and a new primitive called predicate extractable commitment, which may be of independent interest. The talk is based on a joint work with Zuoxia Yu and Willy Susilo.

Inviter: Assoc. Prof. Chengyu Hu