Gao, Y., C. Guo, M. Wang, W. Wang, and J. Wen. “Beyond-Birthday-Bound Security for 4-Round Linear Substitution-Permutation Networks”. IACR Transactions on Symmetric Cryptology, Vol. 2020, no. 3, Sept. 2020, pp. 305-26, doi:10.13154/tosc.v2020.i3.305-326.