Bitcoin Faces Urgent Quantum Risk as 25% of Supply Exposed

Bitcoin’s long-assumed 20-year safety window against quantum computing is collapsing. Roughly 4 million BTC, around 25% of all usable supply, are held in wallets that expose public keys to quantum attacks, according to Deloitte’s January 2026 report.

If attackers use Shor’s algorithm on a sufficiently powerful quantum computer, private keys could be derived instantly, putting dormant wallets at risk and threatening market stability.

Technological progress is accelerating the threat. IBM recently unveiled a new generation of quantum chips, claiming they could achieve quantum advantage by 2026 and early fault-tolerant systems by 2029.

Even Ethereum co-founder Vitalik Buterin has warned that elliptic curve cryptography may break sooner than expected, advocating for Ethereum’s transition to quantum-resistant protocols within a few years. Bitcoin cannot rely on a leisurely multi-decade upgrade path if it hopes to avoid similar vulnerabilities.

Upgrading Bitcoin Will Be Challenging

Switching Bitcoin to quantum-resistant cryptography is not a minor software update; it is a protocol-level overhaul. Researchers from the University of Kent estimate a full migration could take 75 to 300 days, depending on whether the network must operate at reduced capacity to limit attack vectors.

A prolonged downtime for a trillion-dollar asset class carries serious operational and financial risks. Governance adds another layer of complexity. Bitcoin’s upgrade culture is famously resistant to change. Past updates, like Taproot, took years of debate and coordination.

A mandatory migration to quantum-safe cryptography could spark ideological conflicts, potential chain splits, and prolonged uncertainty. Assuming a smooth, decades-long upgrade window is unrealistic given Bitcoin’s history with network-wide changes.

Market Implications of Delayed Action

The market risks of postponing upgrades are significant. If attackers exploit legacy wallets, millions of dormant BTC could flood exchanges, triggering sudden price declines.

Quantum-equipped miners could dominate proof-of-work mining, undermining decentralization and creating an oligopoly. This would reshape the global Bitcoin ecosystem long before any theoretical 20–40 year safe window.

Governments have taken this threat into consideration. The European Commission and individual EU nations issued a plan for post-quantum cryptography earlier this year.

Adoption steps are mandated to begin by 2026, critical infrastructure to be secured by 2030, and the entire PQC migration to take place by 2035. Crypto networks that don’t respond risk severe market difficulties.

Also Read: Bitcoin Faces Growing Regulatory Pushback From Central Banks