Block basis reduction for linear codes in non-Hamming metrics

Overview & Synopsis

In this paper, we generalize the code basis reduction to non-Hamming metrics. We propose a block basis reduction (BKZ) algorithm for codes that works for all coordinate-additive metrics. Our algorithm is a generalization of the algorithm of Ghentiyala and Stephens-Davidowitz, which in turn is an adaptation of the famous BKZ algorithm for lattices to linear codes and the Hamming metric. For block size~$2$ (LLL), we propose a polynomial-time algorithm with complexity~$\mathcal{O}(n^4 q^3)$ operations in~$\mathbb{F}_q$, where~$n$ is the length of the code and~$q$ is the alphabet size. For the Lee metric we provide an implementation of our algorithms and present experimental results on finding low Lee weight codewords.