Syndrome-Based Multi-Bit Error Correction With Chaotic Secure Check-Sequence Sharing for Quantum Key Distribution Systems

Error correction plays a central role in Quantum Key Distribution (QKD) because the raw keys produced by Alice and Bob rarely match exactly. Channel noise, detector fluctuations, and basis mismatches routinely introduce discrepancies that must be resolved before a usable secret key can be formed. Methods such as Cascade and LDPC generally perform well under moderate noise conditions; however, they depend on repeated message exchanges or computationally intensive decoding, which limits their effectiveness when several bits flip together within short time windows. These issues become particularly evident in high-noise environments where correlated errors appear in bursts. To address these challenges, this work presents a syndrome-based multi-bit error-correction technique combined with a chaotic masking approach for securely transmitting the necessary check-sequence data. The technique forms a decimal-summation matrix from each key block and extracts a compact syndrome vector capable of identifying one-, two-, or three-bit errors in a single step. To prevent classical-channel leakage, the required check-sequence is masked using a Tent-map sequence initialized from the entropy associated with the unmatched quantum indices. Simulation results demonstrate a 50–70% reduction in post-correction bit-error rate compared with Cascade, LDPC, and Polar codes across key lengths of 128 to 1024 bits and error probabilities up to 0.5. Overall, the proposed model offers a noise-tolerant and computationally lightweight reconciliation approach and forms the error-correction component of the patented Q-RAPTOR framework (Indian Patent Application No. 202541093982).