Cryptographic Applications of Twisted Goppa Codes
Harshdeep Singh, Anuj Kumar Bhagat, Ritumoni Sarma, Indivar Gupta
TL;DR
The paper defines multi-twisted Goppa (MTG) codes as subfield subcodes of duals of generalized multi-twisted Reed-Solomon codes and proves a distance bound $d \ge t+1$ under suitable conditions. It develops an explicit Extended Euclidean Algorithm–based decoding for MTG codes with twists at arbitrary positions, enabling correction of up to $\left\lfloor t/2 \right\rfloor$ errors, and integrates MTG codes into the Niederreiter cryptosystem with security against partial key-recovery. It also introduces quasi-cyclic MTG constructions to reduce public-key size and provides parameter guidance ensuring post-quantum resilience. The work bridging Goppa-type and RS-type code families yields practical cryptographic schemes with strong structural resistance and scalable key compression strategies, along with a framework for analyzing related attacks and future extensions.
Abstract
This article defines multi-twisted Goppa (MTG) codes as subfield subcodes of duals of multi-twisted Reed-Solomon (MTRS) codes and examines their properties. We show that if $t$ is the degree of the MTG polynomial defining an MTG code, its minimum distance is at least $t + 1$ under certain conditions. Extending earlier methods limited to single twist at last position, we use the extended Euclidean algorithm to efficiently decode MTG codes with a single twist at any position, correcting up to $\left\lfloor \tfrac{t}{2} \right\rfloor$ errors. This decoding method highlights the practical potential of these codes within the Niederreiter public key cryptosystem (PKC). Furthermore, we establish that the Niederreiter PKC based on MTG codes is secure against partial key recovery attacks. Additionally, we also reduce the public key size by constructing quasi-cyclic MTG codes using a non-trivial automorphism group.
