Cryptology ePrint Archive: Report 2022/204

RevEAL: Single-Trace Side-Channel Leakage of the SEAL Homomorphic Encryption Library

Furkan Aydin and Emre Karabulut and Seetal Potluri and Erdem Alkim and Aydin Aysu

Abstract: This paper demonstrates the first side-channel attack on homomorphic encryption (HE), which allows computing on encrypted data. We reveal a power-based side-channel leakage of Microsoft SEAL prior to v3.6 that implements the Brakerski/Fan-Vercauteren (BFV) protocol. Our proposed attack targets the Gaussian sampling in the SEAL’s encryption phase and can extract the entire message with a single power measurement. Our attack works by (1) identifying each coefficient index being sampled, (2) extracting the sign value of the coefficients from control-flow variations, (3) recovering the coefficients with a high probability from data-flow variations, and (4) using a Blockwise Korkine-Zolotarev (BKZ) algorithm to efficiently explore and estimate the remaining search space. Using real power measurements, the results on a RISC-V FPGA implementation of the SEAL (v3.2) show that the proposed attack can reduce the plaintext encryption security level from 2ˆ128 to 2ˆ4.4. Therefore, as HE gears toward real-world applications, such attacks and related defenses should be considered.

Category / Keywords: Side-Channel Attack, Homomorphic Encryption, Microsoft SEAL

Date: received 18 Feb 2022

Contact author: faydn at ncsu edu

Available format(s): PDF | BibTeX Citation

Version: 20220220:204440 (All versions of this report)

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