Event Details

PhD Thesis Proposal - Xinyu Mao

Thu, Oct 02, 2025
12:00 PM - 2:00 PM
Location: GCS 502C
Title: Cryptographic Hash Functinos from Weak to Strong: Collision-Resistance and Universal Computational Extractors
 
Date and Time: Thursday, October 2nd, 2025 | 12:00p - 2:00p
 
Location: GCS 502C
 
Committee Members: Jiapeng Zhang (Chair), David Kempe, Vatsal Sharan, Shanghua Teng, and Jianfeng Zhang   
 
Abstract: Cryptographic hash functions are fundamental primitives in modern cryptography, offering a wide spectrum of security properties from weak to strong. This thesis proposal investigates two significant notions in this spectrum: collision resistance and universal computational extractors. The first part of this work explores relaxations of standard collision-resistant hash functions (CRHs). Our contributions include: A new and arguably the simplest construction of Universal One-Way Hash Functions (UOWHFs), also known as target-collision resistance hash functions, from arbitrary one-way functions (EUROCRYPT 2023). Proposed work to separate Multi-Collision-Resistant Hash Functions (MCRHs) from CRHs. We expect to prove that CRHs cannot be constructed from MCRHs in a black-box manner, meaning that MCRH is a strictly weaker primitive. The second part focuses on Universal Computational Extractors (UCEs), a class of hash functions designed to securely replace the random oracle in various cryptographic schemes. Here, we present the first post-quantum secure (lattice-based) UCE construction that does not rely on indistinguishability obfuscation (EUROCRYPT 2025). Taken together, by providing new constructions and establishing a key separation result, this thesis advances our understanding of various security properties of hash functions.