Code distances of matrix rank-metric codes under Add-and-Remove transformations
Abstract
For a matrix rank-metric code π and an integer i, the i-th subcode distance of π is the largest minimum rank distance of an i-dimensional subcode of π. We study how subcode distances change under the Add-and-Remove construction, in which a subcode of codimension βs is kept and a space of dimension βa is added; this construction is used, with Gabidulin codes, in the MIRANDA signature scheme. For arbitrary matrix codes, we give inequalities between the subcode distances of the original and of the new code, and we show that Delsarte duality interchanges βs and βa. For matrix Gabidulin codes, whose subcode distances are given by an explicit formula, we show that, if βs<max{m,n}, then within each block of indices (aβ1)max{m,n}+1,β¦,amax{m,n} not exceeding dimπ½q(πs), all but the last βs subcode distances are the same as for the Gabidulin code, and the remaining ones decrease by at most one; a small example shows that such a decrease can occur. We also express the minimum distance of the new code in terms of the rank distance between the added space and the common subcode. For MIRANDA, the lower bound on the minimum distance of the dual public code used by the known distinguisher when βs=0 is a special case of these results; for the proposed parameters, where βs>0, the same bound holds for a subcode of codimension βs of the dual public code.
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BibTeX
@misc{alfarano2026code,
title = {{Code distances of matrix rank-metric codes under Add-and-Remove transformations}},
author = {Gianira N. Alfarano and Rakhi Pratihar and Adrien VinΓ§otte},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.03460},
eprint = {2610.03460},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.03460},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Code distances of matrix rank-metric codes under Add-and-Remove transformations
AU - Gianira N. Alfarano
AU - Rakhi Pratihar
AU - Adrien VinΓ§otte
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2610.03460
UR - https://arxiv.org/abs/2610.03460
AB - For a matrix rank-metric code π and an integer i, the i-th subcode distance of π is the largest minimum rank distance of an i-dimensional subcode of π. We study how subcode distances change under the Add-and-Remove construction, in which a subcode of codimension β_s is kept and a space of dimension β_a is added; this construction is used, with Gabidulin codes, in the MIRANDA signature scheme. For arbitrary matrix codes, we give inequalities between the subcode distances of the original and of the new code, and we show that Delsarte duality interchanges β_s and β_a. For matrix Gabidulin codes, whose subcode distances are given by an explicit formula, we show that, if β_s<max{m,n}, then within each block of indices (aβ1)max{m,n}+1,β¦,amax{m,n} not exceeding dim_π½_q(π_s), all but the last β_s subcode distances are the same as for the Gabidulin code, and the remaining ones decrease by at most one; a small example shows that such a decrease can occur. We also express the minimum distance of the new code in terms of the rank distance between the added space and the common subcode. For MIRANDA, the lower bound on the minimum distance of the dual public code used by the known distinguisher when β_s=0 is a special case of these results; for the proposed parameters, where β_s>0, the same bound holds for a subcode of codimension β_s of the dual public code.
ER -