Paper 2019/271

A Simple Key Reuse Attack on LWE and Ring LWE Encryption Schemes as Key Encapsulation Mechanisms (KEMs)

Jintai Ding and Chi Cheng and Yue Qin

Abstract

In this paper, we present a simple attack on LWE and Ring LWE encryption schemes used directly as Key Encapsulation Mechanisms (KEMs). This attack could work due to the fact that a key mismatch in a KEM is accessible to an adversary. Our method clearly indicates that any LWE or RLWE (or any similar type of construction) encryption directly used as KEM can be broken by modifying our attack method according to the respective cases.