AuthorsM. R. Z'aba, H. Raddum, L. Simpson, E. Dawson, M. Henricksen and K. Wong
TitleAlgebraic Analysis of LEX
Afilliation, Communication Systems
Project(s)Simula UiB
Publication TypeProceedings, refereed
Year of Publication2009
Conference NameAustralasian Information Security Conference, AISC2009
ISBN Number978-1-920682-79-8
ISSN Number1445-1336
KeywordsAdvanced Encryption Standard, LEX, Stream Cipher

LEX is a stream cipher that progressed to Phase 3 of the eSTREAM stream cipher project. In this paper, we show that the security of LEX against algebraic attacks relies on a small equation system not being solvable faster than exhaustive search. We use the byte leakage in LEX to construct a system of 21 equations in 17 variables. This is very close to the require- ment for an efficient attack, i.e. a system containing 16 variables. The system requires only 36 bytes of keystream, which is very low.

Citation Key24085