International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Jiaxin Guan

Publications

Year
Venue
Title
2019
EUROCRYPT
Simple Schemes in the Bounded Storage Model 📺
Jiaxin Guan Mark Zhandry
The bounded storage model promises unconditional security proofs against computationally unbounded adversaries, so long as the adversary’s space is bounded. In this work, we develop simple new constructions of two-party key agreement, bit commitment, and oblivious transfer in this model. In addition to simplicity, our constructions have several advantages over prior work, including an improved number of rounds and enhanced correctness. Our schemes are based on Raz’s lower bound for learning parities.
2018
TCC
Return of GGH15: Provable Security Against Zeroizing Attacks
The GGH15 multilinear maps have served as the foundation for a number of cutting-edge cryptographic proposals. Unfortunately, many schemes built on GGH15 have been explicitly broken by so-called “zeroizing attacks,” which exploit leakage from honest zero-test queries. The precise settings in which zeroizing attacks are possible have remained unclear. Most notably, none of the current indistinguishability obfuscation (iO) candidates from GGH15 have any formal security guarantees against zeroizing attacks.In this work, we demonstrate that all known zeroizing attacks on GGH15 implicitly construct algebraic relations between the results of zero-testing and the encoded plaintext elements. We then propose a “GGH15 zeroizing model” as a new general framework which greatly generalizes known attacks.Our second contribution is to describe a new GGH15 variant, which we formally analyze in our GGH15 zeroizing model. We then construct a new iO candidate using our multilinear map, which we prove secure in the GGH15 zeroizing model. This implies resistance to all known zeroizing strategies. The proof relies on the Branching Program Un-Annihilatability (BPUA) Assumption of Garg et al. [TCC 16-B] (which is implied by PRFs in $$\mathsf {NC}^1$$ secure against $$\mathsf {P}/\mathsf {poly}$$) and the complexity-theoretic p-Bounded Speedup Hypothesis of Miles et al. [ePrint 14] (a strengthening of the Exponential Time Hypothesis).

Coauthors

James Bartusek (1)
Fermi Ma (1)
Mark Zhandry (2)