Integrating Post Quantum Cryptography Into Bitcoin Sidechains: A Simulation Based Study

Abstract

The arrival of quantum computing poses a huge threat to conventional public key cryptography used in blockchain systems such as Bitcoin. To address this challenge, we proposes and evaluates a quantum resistant sidechain framework that integrates post quantum digital signature schemes and quantum key distribution (QKD) protocols with the Bitcoin mainchain. Using a Python simulation environment, the performance of multiple signature algorithms. ECDSA as a baseline measurement, Falcon, CRYSTALS-Dilithium, and SPHINCS+ were analyzed in combination with quantum communication protocols BB84, E91, and SARG04. Experimental results show that ECDSA remains the fastest baseline scheme but lacks quantum resistance, while SPHINCS+ provides the highest security with an expected overhead of 93.5 %. Among quantum protocols, BB84 achieved the best overall efficiency across transaction sizes. The optimal integration pairs were BB84 and CRYSTALS-Dilithium combination for speed, security balance and SPHINCS+ and E91 for maximum quantum resilience. These findings demonstrate the practical feasibility of deploying post quantum cryptographic components in Bitcoin compatible sidechains, paving the way for future blockchain networks that remain secure in the post quantum era.