Cryptology ePrint Archive: Report 2019/176

Homomorphic Encryption for Finite Automata

Nicholas Genise and Craig Gentry and Shai Halevi and Baiyu Li and Daniele Micciancio

Abstract: We describe a somewhat homomorphic GSW-like encryption scheme, natively encrypting matrices rather than just single elements. This scheme offers much better performance than existing homomorphic encryption schemes for evaluating encrypted (nondeterministic) finite automata (NFAs). Differently from GSW, we do not know how to reduce the security of this scheme to LWE, instead we reduce it to a stronger assumption, that can be thought of as an inhomogeneous variant of the NTRU assumption. This assumption (that we term iNTRU) may be useful and interesting in its own right, and we examine a few of its properties. We also examine methods to encode regular expressions as NFAs, and in particular explore a new optimization problem, motivated by our application to encrypted NFA evaluation. In this problem, we seek to minimize the number of states in an NFA for a given expression, subject to the constraint on the ambiguity of the NFA.

Category / Keywords: secret-key cryptography / Finite Automata, Inhomogeneous NTRU, Homomorphic Encryption, Regular Expressions.

Original Publication (with minor differences): IACR-ASIACRYPT-2019

Date: received 18 Feb 2019, last revised 16 Mar 2020

Contact author: nicholasgenise at gmail com

Available format(s): PDF | BibTeX Citation

Version: 20200316:234437 (All versions of this report)

Short URL: ia.cr/2019/176