MDS matrix

About: MDS matrix is a research topic. Over the lifetime, 102 publications have been published within this topic receiving 2000 citations.

Direct Construction of Recursive MDS Diffusion Layers Using Shortened BCH Codes

Abstract: MDS matrices allow to build optimal linear diffusion layers in block ciphers. However, MDS matrices cannot be sparse and usually have a large description, inducing costly software/hardware implementations. Recursive MDS matrices allow to solve this problem by focusing on MDS matrices that can be computed as a power of a simple companion matrix, thus having a compact description suitable even for constrained environments. However, up to now, finding recursive MDS matrices required to perform an exhaustive search on families of companion matrices, thus limiting the size of MDS matrices one could look for. In this article we propose a new direct construction based on shortened BCH codes, allowing to efficiently construct such matrices for whatever parameters. Unfortunately, not all recursive MDS matrices can be obtained from BCH codes, and our algorithm is not always guaranteed to find the best matrices for a given set of parameters.

On construction of involutory MDS matrices from Vandermonde Matrices in GF(2q)

Abstract: Due to their remarkable application in many branches of applied mathematics such as combinatorics, coding theory, and cryptography, Vandermonde matrices have received a great amount of attention. Maximum distance separable (MDS) codes introduce MDS matrices which not only have applications in coding theory but also are of great importance in the design of block ciphers. Lacan and Fimes introduce a method for the construction of an MDS matrix from two Vandermonde matrices in the finite field. In this paper, we first suggest a method that makes an involutory MDS matrix from the Vandermonde matrices. Then we propose another method for the construction of 2 n × 2 n Hadamard MDS matrices in the finite field GF(2 q ). In addition to introducing this method, we present a direct method for the inversion of a special class of 2 n × 2 n Vandermonde matrices.

Lightweight MDS Generalized Circulant Matrices

Abstract: In this article, we analyze the circulant structure of generalized circulant matrices to reduce the search space for finding lightweight MDS matrices. We first show that the implementation of circulant matrices can be serialized and can achieve similar area requirement and clock cycle performance as a serial-based implementation. By proving many new properties and equivalence classes for circulant matrices, we greatly reduce the search space for finding lightweight maximum distance separable MDS circulant matrices. We also generalize the circulant structure and propose a new class of matrices, called cyclic matrices, which preserve the benefits of circulant matrices and, in addition, have the potential of being self-invertible. In this new class of matrices, we obtain not only the MDS matrices with the least XOR gates requirement for dimensions from $$3 \times 3$$ to $$8 \times 8$$ in $${\text {GF}}2^4$$ and $${\text {GF}}2^8$$, but also involutory MDS matrices which was proven to be non-existence in the class of circulant matrices. To the best of our knowledge, the latter matrices are the first of its kind, which have a similar matrix structure as circulant matrices and are involutory and MDS simultaneously. Compared to the existing best known lightweight matrices, our new candidates either outperform or match them in terms of XOR gates required for a hardware implementation. Notably, our work is generic and independent of the metric for lightweight. Hence, our work is applicable for improving the search for efficient circulant matrices under other metrics besides XORi¾?gates.

On Constructions of Involutory MDS Matrices

Abstract: Maximum distance separable (MDS) matrices have applications not only in coding theory but also are of great importance in the design of block ciphers and hash functions. It is highly nontrivial to find MDS matrices which is involutory and efficient. In a paper in 1997, Youssef et. al. proposed an involutory MDS matrix construction using Cauchy matrix. In this paper we study properties of Cauchy matrices and propose generic constructions of low implementation cost MDS matrices based on Cauchy matrices. In a 2009 paper, Nakahara and Abrahao proposed a 16 ×16 involutory MDS matrix over \(\mathbb{F}_{2^8}\) by using a Cauchy matrix which was used in MDS-AES design. Authors claimed that their construction by itself guarantees that the resulting matrix is MDS and involutory. But the authors didn’t justify their claim. In this paper we study and prove that this proposed matrix is not an MDS matrix. Note that this matrix has been designed to be used in the block cipher MDS-AES, which may now have severe weaknesses. We provide an algorithm to construct involutory MDS matrices with low Hamming weight elements to minimize primitive operations such as exclusive-or, table look-ups and xtime operations. In a 2012 paper, Sajadieh et. al. provably constructed involutory MDS matrices which were also Hadamard in a finite field by using two Vandermonde matrices. We show that the same matrices can be constructed by using Cauchy matrices and provide a much simpler proof of their construction.

Exhaustive search for small dimension recursive MDS diffusion layers for block ciphers and hash functions

Abstract: This article presents a new algorithm to find MDS matrices that are well suited for use as a diffusion layer in lightweight block ciphers. Using an recursive construction, it is possible to obtain matrices with a very compact description. Classical field multiplications can also be replaced by simple F2-linear transformations (combinations of XORs and shifts) which are much lighter. Using this algorithm, it was possible to design a 16×16 matrix on a 5-bit alphabet, yielding an efficient 80-bit diffusion layer with maximal branch number.