Cryptology ePrint Archive: Report 2020/015

Efficient Homomorphic Conversion Between (Ring) LWE Ciphertexts

Hao Chen and Wei Dai and Miran Kim and Yongsoo Song

Abstract: In the past few years, significant progresses on homomorphic encryption (HE) have been made toward both theory and practice. The most promising HE schemes are based on the hardness of the Learning With Errors (LWE) problem or its ring variant (RLWE). In this work, we present new conversion algorithms which switch between different (R)LWE-based HE schemes to take advantages of them. Specifically, we present and combine three ideas to improve the key-switching procedure between LWE ciphertexts, transformation from LWE to RLWE, as well as packing of multiple LWE ciphertexts in a single RLWE encryption. Finally, we demonstrate an application of building a secure channel between a client and a cloud server with lightweight encryption, low communication cost, and capability of homomorphic computation.

Category / Keywords: public-key cryptography / Homomorphic encryption; Learning with Errors; Key switching

Date: received 5 Jan 2020, last revised 22 Jan 2020

Contact author: yongsoo song at microsoft com

Available format(s): PDF | BibTeX Citation

Version: 20200122:232749 (All versions of this report)

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