Multiple right-hand side (MRHS) equations over finite fields are a relatively
new tool useful for algebraic cryptanalysis. The main advantage is in an efficient
representation of the cryptographic primitives. The main methods to solve systems of MRHS
equations are gluing, that relies on merging equations, and various versions of local reduction,
that relies on removing partial solutions.
In this paper we present a new algorithm to solve MRHS systems. The core of the algorithm is
a transformation of the problem of solving an MRHS equation system into a problem of group factorization.
We then provide two alternative algorithms to solve the transformed problem. One of these algorithms
provides a further transformation to the well-studied closest vector problem.
A corollary of our research is that the solution of the group factorization problem
arising during the process of solving an MRHS equation system must be as difficult as the cryptanalysis
of a corresponding block cipher described by this MRHS system.
JMC is a forum for original research articles in the area of mathematical cryptology. Works in the theory of cryptology and articles linking mathematics with cryptology are welcome. Submissions from all areas of mathematics significant for cryptology are published, including but not limited to, algebra, algebraic geometry, coding theory, combinatorics, number theory, probability and stochastic processes.