Nine crypto organizations have created the Quantum Alliance to define common standards to protect blockchains against future quantum computers. The group estimates that 6.04 million BTC already have a visible public key, but these funds cannot be stolen with the machines available today.
In brief
- Nine crypto organizations create the Quantum Alliance to prepare blockchains for future quantum threats.
- More than 6 million BTC could become vulnerable, but no current quantum computer can hack them.
- The Quantum Alliance wants to establish common standards to strengthen the security of blockchains and wallets.
- The arrival of Q-Day remains uncertain, despite certain forecasts which suggest a threat as early as 2028.
- The migration to post-quantum cryptography raises technical challenges, particularly for lost or inactive bitcoins.
More than 6 million bitcoins would eventually be exposed
The threat concerns the cryptography that proves ownership of bitcoins, not the general functioning of the blockchain. Bitcoin uses signatures based on elliptic curves to verify that a transaction has been authorized by the holder of a private key.
Several points make it possible to measure the exact nature of the risk:
- Around 6.04 million BTC would have a public key already visible;
- This amount represents nearly 30.2% of the existing supply;
- Some broader calculations suggest between 6.4 and 6.9 million BTC;
- Bitcoins attributed to Satoshi Nakamoto could be part of the funds affected;
- No current quantum computer can find a Bitcoin private key.
A public key allows other users to verify a signature. Classical computers cannot transform it into a private key in a realistic time frame. A future error-corrected quantum machine could, however, apply Shor’s algorithm to solve this mathematical problem.
Estimates differ depending on the types of addresses and the method used. Some calculations only count outputs whose public key appears directly on the blockchain. Others add reused addresses, funds associated with old formats, or certain bitcoins protected by Taproot.
The expression “exposed bitcoins” therefore describes a potential long-term vulnerability. It does not mean that 6 million BTC are today accessible to pirates.
The Quantum Alliance wants to define verifiable standards
The Quantum Alliance brings together representatives from Quantus, American Fortress, Intmax, Keystone, Midnight Foundation, Postquant Labs, Abelian, The Vault and Hacken. Its members are involved in blockchains, hardware wallets, cybersecurity, zero-knowledge proofs and quantum infrastructure.
The group is modeled after the Internet Engineering Task Force, which develops open technical standards for the Internet. Its proposals must be based on public evidence, approximate consensus and functional implementations. The size of a company or the quantity of tokens it holds will not give it more weight.
The work will be divided between four groups dedicated to blockchain migration, post-quantum zero-knowledge systems, wallet security and cross-network compatibility. The Alliance must publish criteria which will make it possible to verify whether a project is really “quantum-ready”.
This clarification responds to a current weakness in the sector. A blockchain can present itself as resistant to quantum computers without specifying whether this protection covers signatures, consensus, bridges, oracles or the keys used to issue stablecoins.
Christopher Smith, founder of Quantus, says:
In the future, post-quantum cryptography will just be called cryptography, and everything else will be in a museum.
He wants to prepare standards now that projects can adopt during their migration.
The date of Q-Day remains impossible to predict
The Quantum Alliance cites several estimates that place a first practical attack around the end of the 2020s. “Quantum Doom Clock” created by two of its contributors designates March 2028 as the first possible window.
This date does not represent a scientific consensus. Other specialists are looking more towards the 2030s, while the necessary progress in error correction and the production of logical qubits remains considerable.
A Google study published in 2026 estimates that a machine with fewer than 500,000 physical qubits could, under certain assumptions, break the elliptical cryptography used by Bitcoin in a few minutes. This calculation describes a future architecture. Current processors remain far too small and unstable to execute such an attack.
The real challenge concerns migration. New post-quantum signatures could protect funds transferred to suitable addresses. They would not automatically solve the case of lost wallets, deceased owners or holders who never move their bitcoins.
Proposal BIP-361 envisages a gradual transition to new signatures, then a restriction of old ones. It raises a sensitive question: should we freeze coins that do not migrate to prevent their theft, at the risk of modifying the rights attached to legitimately held bitcoins?
The Alliance will not be able to impose a response to Bitcoin, whose rules evolve by consensus. Its usefulness will lie above all in the creation of common tests and comparable migration methods. The threat remains theoretical, but the time required for a global upgrade justifies preparing for this transition well in advance of the arrival of a machine capable of attacking the keys.
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