International Association
for Cryptologic Research

Simeck is a new family of lightweight block ciphers proposed by Yang $et\ al.$ in CHES'15, which has efficient hardware implementation. In this paper, we find differentials with low hamming weight and high probability for Simeck using K\"olbl's tool, then we consider the links between the differential and linear characteristic to construct linear hulls for Simeck. We give improved linear hull attack with dynamic key-guessing techniques on Simeck according to the property of the AND operation. Our best results cover Simeck 32/64 reduced to 23 rounds, Simeck 48/96 reduced to 30 rounds, Simeck 64/128 reduced to 37 rounds. Our result is the best known so far for any variant of Simeck.