Cryptology ePrint Archive: Report 2020/1395

Post-Quantum Multi-Party Computation

Amit Agarwal and James Bartusek and Vipul Goyal and Dakshita Khurana and Giulio Malavolta

Abstract: We initiate the study of multi-party computation for classical functionalities (in the plain model) with security against malicious polynomial-time quantum adversaries. We observe that existing techniques readily give a polynomial-round protocol, but our main result is a construction of constant-round post-quantum multi-party computation. We assume mildly super-polynomial quantum hardness of learning with errors (LWE), and polynomial quantum hardness of an LWE-based circular security assumption. Along the way, we develop the following cryptographic primitives that may be of independent interest:

- A spooky encryption scheme for relations computable by quantum circuits, from the quantum hardness of an LWE-based circular security assumption. This yields the first quantum multi-key fully-homomorphic encryption scheme with classical keys. - Constant-round zero-knowledge secure against multiple parallel quantum verifiers from spooky encryption for relations computable by quantum circuits. To enable this, we develop a new straight-line non-black-box simulation technique against parallel verifiers that does not clone the adversary's state. This forms the heart of our technical contribution and may also be relevant to the classical setting. - A constant-round post-quantum non-malleable commitment scheme, from the mildly super-polynomial quantum hardness of LWE.

Category / Keywords: cryptographic protocols / multi-party computation, post-quantum

Date: received 8 Nov 2020

Contact author: bartusek james at gmail com

Available format(s): PDF | BibTeX Citation

Version: 20201110:125632 (All versions of this report)

Short URL: ia.cr/2020/1395


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