International Association for Cryptologic Research

International Association
for Cryptologic Research


Jiapeng Zhang


Simple Constructions from (Almost) Regular One-Way Functions 📺
Noam Mazor Jiapeng Zhang
Two of the most useful cryptographic primitives that can be constructed from one-way functions are pseudorandom generators (PRGs) and universal one-way hash functions (UOWHFs). In order to implement them in practice, the efficiency of such constructions must be considered. The three major efficiency measures are: the seed length, the call complexity to the one-way function, and the adaptivity of these calls. Still, the optimal efficiency of these constructions is not yet fully understood: there exist gaps between the known upper bound and the known lower bound for black-box constructions. A special class of one-way functions called unknown-regular one-way functions is much better understood. Haitner, Harnik and Reingold (CRYPTO 2006) presented a PRG construction with semi-linear seed length and linear number of calls based on a method called randomized iterate. Ames, Gennaro and Venkitasubramaniam (TCC 2012) then gave a construction of UOWHF with similar parameters and using similar ideas. On the other hand, Holenstein and Sinha (FOCS 2012) and Barhum and Holenstein (TCC 2013) showed an almost linear call-complexity lower bound for black-box constructions of PRGs and UOWHFs from one-way functions. Hence Haitner et al. and Ames et al. reached tight constructions (in terms of seed length and the number of calls) of PRGs and UOWHFs from regular one-way functions. These constructions, however, are adaptive. In this work, we present non-adaptive constructions for both primitives which match the optimal call-complexity given by Holenstein and Sinha and Barhum and Holenstein. Our constructions, besides being simple and non-adaptive, are robust also for almost-regular one-way functions.
Unifying Presampling via Concentration Bounds 📺
Siyao Guo Qian Li Qipeng Liu Jiapeng Zhang
Auxiliary-input (AI) idealized models, such as auxiliary-input random oracle model (AI-ROM) and auxiliary-input random permutation model (AI-PRM), play a critical role in assessing non-uniform security of symmetric key and hash function constructions. However, obtaining security bounds in these models is often much more challenging. The presampling technique, introduced by Unruh (CRYPTO' 07), generically reduces security proofs in the auxiliary-input models to much simpler bit-fixing models. This technique has been further optimized by Coretti, Dodis, Guo, Steinberger (EUROCRYPT' 18), and generalized by Coretti, Dodis, Guo (CRYPTO' 18), resulting in powerful tools for proving non-uniform security bounds in various idealized models. We study the possibility of leveraging the presampling technique to the quantum world. To this end, (*) We show that such leveraging will {resolve a major open problem in quantum computing, which is closely related to the famous Aaronson-Ambainis conjecture (ITCS' 11). (*) Faced with this barrier, we give a new but equivalent bit-fixing model and a simple proof of presampling techniques for arbitrary oracle distribution in the classical setting, including AI-ROM and AI-RPM. Our theorem matches the best-known security loss and unifies previous presampling techniques. (*) Finally, we leverage our new classical presampling techniques to a novel ``quantum bit-fixing'' version of presampling. It matches the optimal security loss of the classical presampling. Using our techniques, we give the first post-quantum non-uniform security for salted Merkle-Damgard hash functions and reprove the tight non-uniform security for function inversion by Chung et al. (FOCS' 20).


Siyao Guo (1)
Qian Li (1)
Qipeng Liu (1)
Shachar Lovett (1)
Noam Mazor (1)
Bo Tang (2)