Recovering Internal States of Grain-v1

Abstract

In this paper, we analyze the non-linear part of the output function h of Grain-v1 and use a guess and determine strategy to recover 33 state bits from 33 consecutive keystream bits of Grain-v1 by fixing 45 bits and guessing 82 bits. This reduces the conditional sampling resistance of Grain-v1, which is best till now. We apply the Time-Memory-Data Trade-Off (TMDTO) attack on Grain-v1 with this conditional sampling resistance to get a trade-off curve which improves the pre-processing time complexity and online time complexity with improved memory.