Quantum Disruption: An SOK of How Post-Quantum Attackers Reshape Blockchain Security and Performance

Abstract

As quantum computing advances, classical cryptographic systems - signature schemes, key exchange protocols, public-key encryption, and certain hash constructions - that secure most blockchain platforms come under threat, raising serious concerns about their long-term security and integrity. Transitioning to post-quantum primitives is rarely straightforward: their larger sizes and higher computation costs can have unintended consequences, and in some cases make such a transition impractical. We examine the impact of post-quantum migration on blockchain systems across three dimensions. First, we dissect the cryptographic primitives most vulnerable to quantum attacks within the consensus, identity, and transaction-validation layers. Next, we survey proposed post-quantum adaptations and evaluate their practical feasibility. Finally, we assess how substituting classical primitives with post-quantum alternatives affects system performance, protocol behavior, and the underlying incentive and trust structures. Our findings show that PQ adoption is far from a drop-in replacement: it demands careful architectural reconsideration, as naive substitution risks destabilizing core protocol operations and weakening the security and efficiency guarantees blockchains rely upon.