[Resource Topic] 2024/274: Amortized Large Look-up Table Evaluation with Multivariate Polynomials for Homomorphic Encryption

Welcome to the resource topic for 2024/274

Title:
Amortized Large Look-up Table Evaluation with Multivariate Polynomials for Homomorphic Encryption

Authors: Heewon Chung, Hyojun Kim, Young-Sik Kim, Yongwoo Lee

Abstract:

We present a new method for efficient look-up table (LUT) evaluation in homomorphic encryption (HE), based on Ring-LWE-based HE schemes, including both integer-message schemes such as Brakerski-Gentry-Vaikuntanathan (BGV) and Brakerski/Fan-Vercauteren (BFV), and complex-number-message schemes like the Cheon-Kim-Kim-Song (CKKS) scheme. Our approach encodes bit streams into codewords and translates LUTs into low-degree multivariate polynomials, allowing for the simultaneous evaluation of multiple independent LUTs with minimal overhead. To mitigate noise accumulation in the CKKS scheme, we propose a novel noise-reduction technique, accompanied by proof demonstrating its effectiveness in asymptotically decreasing noise levels.
We demonstrate our algorithm’s effectiveness through a proof-of-concept implementation, showcasing significant efficiency gains, including a 0.029ms per slot evaluation for 8-input, 8-output LUTs and a 280ms amortized decryption time for AES-128 using CKKS on a single GPU. This work not only advances LUT evaluation in HE but also introduces a transciphering method for the CKKS scheme utilizing standard symmetric-key encryption, bridging the gap between discrete bit strings and numerical data.

ePrint: https://eprint.iacr.org/2024/274

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