International Association
for Cryptologic Research

Lightweight cryptography is an emerging field that will play a critical role in areas like pervasive computing and Internet of Things (IoT). In recent years, many lightweight ciphers have been designed that are better suited for small scale embedded security. Lightweight ciphers like PRESENT, KLEIN, Hummingbird 2, XTEA, CLEFIA etc. are the ciphers known for compact hardware implementations. Recently SIMON and SPECK ciphers have been introduced which are Feistel based designs. SIMON and SPECK are flexible and are having very less memory requirements and better performance in both hardware and software. There is always a tradeoff between security and performance. Strengthening the design of these ciphers will increase their acceptability for all embedded applications. In this paper, we have proposed a novel approach which increases the strength and performance of SIMON and SPECK. Further a confusion layer is added in the design of the newly designed cipher RECTANGLE. RECTANGLE has a robust S-box as compared to other lightweight ciphers which makes the design fast and efficient. We have added the substitution property to the SIMON and SPECK cipher after analyzing the cryptanalysis properties of both the ciphers. S-box of RECTANGLE is best suited for SIMON and SPECK because the SIMON and SPECK designs have an asymmetric permutation which is the basic requirement for RECTANGLE. Combination of S-box and asymmetric permutation together achieves a robust design. The hybrid design proposed in this paper needs less memory space as compared to the existing ciphers. This approach makes SIMON and SPECK design more robust and resistive against all possible attacks due to the addition of the non-linear substitution layer. This robust design will have a positive impact in the field of lightweight cryptosystems.