High Memory Masked Convolutional Codes for PQC

This paper presents a novel post-quantum cryptosystem based on high-memory masked convolutional codes. Unlike conventional code-based schemes that rely on block codes with fixed dimensions and limited error-correction capability, our construction offers both stronger cryptographic security and greater flexibility. It supports arbitrary plaintext lengths with linear-time decryption and uniform per-bit computational cost, enabling seamless scalability to long messages. Security is reinforced through a higher-rate injection of random errors than in block-code approaches, along with additional noise introduced via polynomial division, which substantially obfuscates the underlying code structure. Semi-invertible transformations generate dense, random-like generator matrices that conceal algebraic properties and resist known structural attacks. Consequently, the scheme achieves cryptanalytic security margins exceeding those of the classic McEliece system by factors greater than 2100. Finally, decryption at the recipient employs an array of parallel Viterbi decoders, enabling efficient hardware and software implementation and positioning the scheme as a strong candidate for deployment in practical quantum-resistant public-key cryptosystems.