eSPF: A Family of Format-Preserving Encryption Algorithms Using MDS Matrices

Donghoon Chang, Mohona Ghosh, Arpan Jati, Abhishek Kumar, Somitra Kumar Sanadhya

Abstract: The construction SPF, presented in Inscrypt-2016 was the first known SPN based format-preserving encryption algorithm. In this work, we significantly improve its performance and flexibility. We term this new construction as eSPF. Unlike SPF, all the basic transformations of eSPF are defined under the field \(\mathbb {F}_p\). This allows us to use a MDS matrix instead of the binary matrix used in SPF. The optimal diffusion of MDS matrix leads to an efficient and secure design. However, this change leads to violations in the message format. To mitigate this, we propose a discarding algorithm to drop the symbols that are not the elements of the format thus preserving it.