Comprehensive study of integral analysis on LBlock

Abstract

The current paper presents an integral cryptanalysis in the single-key setting against light-weight block-cipher LBlock reduced to 22 rounds. Our attack uses the same 15-round integral distinguisher as the previous attacks, but many techniques are taken into consideration in order to achieve comprehensive understanding of the attack; choosing the best balanced-byte position, meet-in-the-middle technique to identify right key candidates, partial-sum technique, relations among subkeys, and combination of the exhaustive search with the integral analysis. Our results indicate that the integral cryptanalysis is particularly useful for LBlock like structures. At the end of this paper, which factor makes the LBlock structure weak against the integral cryptanalysis is discussed. Because designing light-weight cryptographic primitives is an actively discussed topic, we believe that this paper returns some useful feedback to future designs.