High‐throughput and flexible ASIC implementations of SIMON and SPECK lightweight block ciphers

Abstract

In this paper, high-throughput and flexible hardware implementations of the SIMON and SPECK lightweight block ciphers are presented. The most complex block in the SPECK algorithm is addition modulo 2 n , where n is word size (half of the input data). In the proposed structure of modular adder, we used the Sklansky adder, which is an efficient parallel prefix adder with low critical path delay and suitable hardware resources. In the SIMON block cipher, to reduce critical path delay, we use a tree structure for implementation of XOR operations.In addition, we proposed flexible structures that can perform various configurations of the SIMON and SPECK ciphers to support variable key sizes (128, 144, 192, and 256 bits) and block sizes (64, 96, and 128 bits). Therefore, the flexible architectures provide versatile implementations with adaptive security level and the ability of encryption of longer messages based on variable key size and variable block size. Implementation results of the proposed structures in 180 nm CMOS technology for different key and block sizes are achieved. The results show that the proposed structures have better critical path delay compared with other's related works. KEYWORDS ASIC, high throughput, lightweight, SIMON block cipher, SPECK block cipher INTRODUCTIONLightweight cryptography has been an important area of cryptographic research in recent years. Different lightweight block ciphers with various design strategies have been presented. 1-3 The advanced encryption standard (AES) is one of the most important and applicable block ciphers in hardware and software. 4 For low-resource devices, the AES is a too expensive block cipher. Therefore, many lightweight block ciphers have been proposed to reduce the costs of hardware consumption than that of AES. Lightweight block cipher algorithms play an important role in the security for resource-constrained devices, such as radio frequency identification (RFID) tags, smart cards, and wireless sensor network (WSN) nodes. SIMON and SPECK 5,6 are lightweight block cipher families with 32 to 128 bits block size and 64 to 256 bits key length, which are suitable for lightweight hardware implementation such as embedded CPUs that are used in the low-area cryptographic application systems. These block ciphers were developed by the National Security Agency (NSA) 5,6 to provide flexibility and security in lightweight applications. These ciphers have been submitted to the International Organization for Standardization (ISO) for inclusion in the ISO 29192-2 standard. The number of rounds in SIMON cipher ranges from 32 rounds to 72 rounds. This cipher has a simple structure based on bit-wise XOR, bit-wise AND, and rotation operations. Also, variants of SPECK block cipher exist for different parameters of key size, block size, 1254

Flexible structures of lightweight block ciphers PRESENT, SIMON and LED

“…In [26] three structures of the SIMON cipher (iterative structure, keyagile pipeline structure, and non-key-agile pipeline structure) are presented. In [30] a flexible SIMON block cipher is presented. To reduce CPD, a tree structure for implementation of the XOR operations is used.…”

“…It requires 39 clock cycles to perform one round of LED, the final result is achieved in a total latency of 1248 clock cycles for LED-64 and 1872 clock cycles for LED-128. The results of the proposed implementation on flexible SIMON cipher and flexible structure in work [30] for several special cases are presented in Table 10. The proposed structure has better results in terms of area consumption (Table 9) and Thr./area (Table 10).…”

“…Also, the S‐box is implemented based on an area‐optimisedcombinational logic circuit by using the Karnaugh mapping and further factorisation.In [26] three structures of the SIMON cipher(iterative structure, key‐agile pipeline structure, and non‐key‐agile pipelinestructure) are presented. In [30] a flexibleSIMON block cipher is presented. To reduce CPD, a tree structure for implementationof the XOR operations is used.…”

“…Also, the S-box is implemented based on an area-optimised combinational logic circuit by using the Karnaugh mapping and further factorisation. The works [26][27][28][29][30] presented the ASIC implementations of the SIMON cipher. In [26] three structures of the SIMON cipher (iterative structure, key-agile pipeline structure, and non-key-agile pipeline structure) are presented.…”

“…In [29] a bit‐serialised SIMON structure with 32‐bit plaintext and the 64‐bit key is proposed. In [30] a flexible SIMON block cipher is presented. To reduce critical path delay (CPD), a tree structure for the implementation of XOR operations is used.…”