Paper 2020/038

Bitstream Modification Attack on SNOW 3G

Michail Moraitis and Elena Dubrova

Abstract

SNOW 3G is one of the core algorithms for confidentiality and integrity in several 3GPP wireless communication standards, includ- ing the new Next Generation (NG) 5G. It is believed to be resistant to classical cryptanalysis. In this paper, we show that SNOW 3G can be broken by a fault attack based on bitstream modification. By changing the content of some look-up tables in the bitstream, we reduce the non- linear state updating function of SNOW 3G to a linear one. As a result, it becomes possible to recover the key from the keystream. To our best knowledge, this is the first successful bitstream modification attack on SNOW 3G. We propose a countermeasure which blows-up the number of candidate points for fault injection, making the presented attack infeasible in practice.