Developers are warning that a growing quantum computing threat could compromise 25% of Bitcoin’s supply due to exposed public keys.

To combat this, Jameson Lopp, CTO and co-founder of self-custody service Casa, has proposed a quantum-resistant upgrade to the cryptocurrency’s software.

A Three-Phase Solution

According to a July 15 Bitcoin Improvement Proposal (BIPs), approximately 4 million BTC, including the 1 million believed to belong to Satoshi Nakamoto, are vulnerable to future quantum computer attacks.

“Bitcoins current signatures (ECDSA/Schnorr) will be a tantalizing target: any UTXO that has ever exposed its public key on-chain (roughly 25% of all bitcoin) could be stolen by a cryptographically relevant quantum computer,” the post said.

The plan outlines three steps to reduce this threat. The first phase would block users from sending BTC to quantum-vulnerable addresses and instead require the use of a new post-quantum address type called P2QRH.

The second step, planned to begin two years later, would freeze any funds that have not been moved to a secure address. The final phase is still being studied and could allow people to recover frozen assets using a BIP-39 seed phrase.

Lopp presented the initiative at the Quantum Bitcoin Summit in San Francisco, an invite-only gathering of experts focused on protecting BTC against such vulnerabilities. The plan, crafted in collaboration with five other developers, is built around an incentive mechanism that warns users they will lose access to their funds if they do not upgrade. The goal is to push holders toward safer storage methods that quantum computers cannot compromise.

The Quantum Threat

In the proposal, the authors stressed the enormity of the threat posed to the Bitcoin ecosystem by a potential quantum attack:

“Never before has Bitcoin faced an existential threat to its cryptographic primitives,” they wrote. “A successful quantum attack on Bitcoin would result in significant economic disruption and damage across the entire ecosystem.”

Their fear is backed by a past Deloitte study explaining how severe the damage could be. The research demonstrated that if the vulnerable BTC were unlocked and sold following a quantum attack, it would trigger heavy selling pressure on the market. Lopp described this situation as a “liquidation event.”

Elsewhere, Project Eleven, a research group focused on quantum computing, recently announced a competition to measure the real-world risk such technology poses to the leading cryptocurrency’s security.

The group reported that more than 10 million BTC addresses have exposed public keys. This puts about 6.2 million BTC, worth around $500 billion, at risk if quantum computing continues to improve. A separate analysis by CryptoQuant pointed out that these attacks could also affect mining operations.