A review of design approaches for lightweight block cryptosystems and new lightweight binary matrices

Different concepts of lightweight XSL-based block ciphers are considered in this article. We stress some important aspects: using tweaks are widespread due to providing more randomization and side-channel protection; key schedules should be nontrivial, but not so complex; S-boxes should have good cryptographic properties and implementation cost, and to resist linear and differential cryptanalysis, it is important to analyze them together with the linear transformation. An interesting observation is that MDS linear transformations appear to be a suboptimal choice. Binary matrices offer a much more efficient implementation, and the number of active S-boxes in an XSL-scheme with a binary matrix proves sufficient. Using MILP method we obtain new binary $$4 \times 4$$ matrices that can be implemented with 2 and 3 field XORs and exhibit competitive number of active S-boxes (96 and 102 per 25 rounds resp.) in XSL-scheme.