RECTANGLE: A Bit-slice Ultra-Lightweight Block Cipher Suitable for Multiple Platforms

In this paper, we propose a new lightweight block cipher named RECTANGLE. The main idea of the design of RECTANGLE is to allow lightweight and fast implementations using bit-slice techniques. RECTANGLE uses an SPnetwork. The substitution layer consists of 16 4×4 S-boxes in parallel. The permutation layer is composed of 3 rotations. As shown in this paper, RECTANGLE offers great performance in both hardware and software environment, which proves enough flexibility for different application scenario. The following are 3 main advantages of RECTANGLE. First, RECTANGLE is extremely hardwarefriendly. For the 80-bit key version, a one-cycle-per-round parallel implementation only needs 1467 gates for a throughput of 246 Kbits/sec at 100KHz clock and an energy efficiency of 1.11 pJ/bit. Second, RECTANGLE achieves a very competitive software speed among the existing lightweight block ciphers due to its bit-slice style. Using 128-bit SSE instructions, a bit-slice implementation of RECTANGLE reaches an average encryption speed of about 5.38 cycles/byte for messages around 1000 bytes. Last but not least. We propose new design criteria for 4×4 S-boxes. RECTANGLE uses such a new type of S-box. Due to our careful selection of the S-box and the asymmetric design of the permutation layer, RECTANGLE achieves a very good security-performance tradeoff. Our extensive and deep security analysis finds distinguishers for up to 14 rounds only, and the highest number of rounds that we can attack, is 18 (out of 25).