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The reshaping of a block matrix vectorizes, transposes and stacks on top of each other the blocks of the matrix itself. This paper investigates the statistical applications of matrix reshaping to three-way data, partial traces and measures of multivariate shape. [ABSTRACT FROM AUTHOR]

In this paper we describe a cryptanalysis of a key exchange scheme recently proposed by Álvarez, Tortosa, Vicent and Zamora. The scheme is based on exponentiation of block matrices over a finite field of prime order, and its security is claimed to rely in the hardness of a discrete logarithm problem in a subgroup of . However, the proposal’s design allows for a clean attack strategy which exploits the fact that exponents are at some point added instead of multiplied as in a standard Diffie–Hellman construction. This strategy is moreover successful for a much more general choice of parameters than that put forward by Álvarez et al. [ABSTRACT FROM AUTHOR]