FUTURE: A Lightweight Block Cipher Using an Optimal Diffusion Matrix

Abstract

AbstractIn this work, we present FUTURE, a new 64-bit lightweight SPN-based block cipher. FUTURE encrypts data in a single clock cycle with a very low implementation cost compared to other block ciphers in unrolled fashion. The advantage of an unrolled implementation is that there are no sequential elements, such as registers, in the implementation and hence no clock. While designing FUTURE in a completely unrolled fashion, the goal was to keep the implementation costs low along with minimal latency. Security is the most essential aspect of a cryptographic primitive. However, in addition to security, an essential secondary criterion for a lightweight cryptographic primitive is efficient implementation in hardware and software. Most lightweight block ciphers refrain from the use of MDS matrices in the round function, and as a result, they need more rounds for full encryption. Using MDS matrices in a lightweight block cipher is a challenging task due to its high implementation cost. The lightweight block cipher FUTURE overcomes this challenge by judiciously choosing a very lightweight MDS matrix, which is a composition of 4 sparse matrices. We also use a lightweight cryptographically significant Sbox which is a composition of 4 Sboxes.KeywordsLightweight cryptographyBlock cipherSubstitution-permutation networkMDS matrix