Security of Khudra Against Meet‐in‐the‐Middle‐Type Cryptanalysis

Abstract

Khudra is a lightweight block cipher proposed in SPACE 2014. The cipher is designed for Field programmable gate array (FPGA) based platforms. In this paper, we introduce the first biclique attack on full Khudra in the single key setting, with time complexity of 278.3 encryptions. The time complexity can be further reduced if the post-whitening key is omitted. Furthermore, based on the bicliques constructed, Meet-in-the-middle(MITM) attack is applied to 15-round Khudra, and the best result of Khudra in terms of attacked rounds against MITM attack is achieved.