Bitcoin's Post-Quantum Dilemma: Scalability Crisis Looms as Quantum Risk Compresses

The crypto industry is facing a scalability and governance crisis as it transitions to a post-quantum future. According to a new report from quantum-secure blockchain project Quantus, Bitcoin (BTC) and other legacy chains may struggle to migrate before quantum hardware reaches dangerous capability thresholds.

The report warns that the industry's biggest problem is no longer whether quantum computers will eventually break classical cryptography, but rather whether decentralized networks can coordinate a migration to post-quantum systems without overwhelming scalability limits, wallet infrastructure, and governance processes. Bitcoin's post-quantum upgrade could lead to a 74-fold increase in transaction size, sharply reducing capacity per block unless the network undergoes deeper architectural changes.

The report estimates that the burden of migrating to post-quantum systems could become severe for Bitcoin. Auryn Macmillan, co-founder of Gnosis Guild, suggested that a hard deadline for account owners to migrate their tokens to quantum-safe accounts may be necessary, potentially forcing users to migrate assets under protocol-imposed timelines.

The report also warns that hardware limitations and public keys already exposed onchain remain permanently visible, creating a lasting attack surface for older wallets and reused addresses. The industry has often treated quantum risk as distant, but researchers argue the timeline is compressing faster than expected.