On the hull and complementarity of one generator quasi-cyclic codes and four-circulant codes
Zohreh Aliabadi, Cem Güneri, Tekgül Kalaycı
TL;DR
This work analyzes the hull and complementarity properties of two quasi-cyclic code families: one-generator QC codes and four-circulant codes. It develops explicit hull-dimension formulas expressed in terms of generating and parity-check polynomials, and provides complete LCD and LCP characterizations by leveraging a CRT-based decomposition into constituents. Notably, FC codes have even hull dimensions, and DC codes cannot have hull dimension 1 when $q \equiv 3 \pmod{4}$; the paper also gives necessary conditions (and counterexamples) for LCD status and describes LCP criteria for both classes. Computational results for binary and ternary cases illustrate near-optimal LCD/LCP parameters and hull-1 hull behavior, highlighting practical implications for cryptography and quantum-code constructions.
Abstract
We study one generator quasi-cyclic codes and four-circulant codes, which are also quasi-cyclic but have two generators. We state the hull dimensions for both classes of codes in terms of the polynomials in their generating elements. We prove results such as the hull dimension of a four-circulant code is even and one-dimensional hull for double-circulant codes, which are special one generator codes, is not possible when the alphabet size $q$ is congruent to 3 mod 4. We also characterize linear complementary pairs among both classes of codes. Computational results on the code families in consideration are provided as well.
