Quantum Alliance Targets Bitcoin’s Future Security

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 machines available today.

More than 6 million bitcoins could eventually be exposed

The threat concerns the cryptography that proves bitcoin ownership, not the general operation of the blockchain. Bitcoin uses signatures based on elliptic curves to verify that a transaction has indeed been authorized by the holder of a private key.

Several points help measure the exact nature of the risk :

• About 6.04 million BTC supposedly have a public key already visible ;
• This amount represents nearly 30.2% of the existing supply ;
• Some broader calculations estimate between 6.4 and 6.9 million BTC ;
• Bitcoins attributed to Satoshi Nakamoto could be among the affected funds ;
• No current quantum computer can retrieve a Bitcoin private key.

A public key allows other users to verify a signature. Classical computers cannot turn it into a private key within a realistic timeframe. A future error-corrected quantum machine could, however, apply Shor’s algorithm to solve this mathematical problem.

Estimates vary depending on address types and method used. Some calculations count only outputs where the public key appears directly on the blockchain. Others add reused addresses, funds associated with old formats, or certain bitcoins secured by Taproot.

The term “exposed bitcoins” thus describes a potential long-term vulnerability. It does not mean that 6 million BTC are currently accessible to hackers.

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 work in blockchains, hardware wallets, cybersecurity, zero-knowledge proofs, and quantum infrastructures.

The group is inspired by the Internet Engineering Task Force, which develops open technical standards for the Internet. Its proposals will have to rely on public evidence, rough consensus, and functional implementations. A company’s size or the amount of tokens it holds will not give it more weight.

The work will be divided into four groups focused on blockchain migration, post-quantum zero-knowledge systems, wallet security, and cross-network compatibility. The Alliance must publish criteria to verify if a project is truly “quantum-ready”.

This clarification addresses a current weakness of the sector. A blockchain can claim to be quantum-resistant without specifying whether this protection covers signatures, consensus, bridges, oracles, or keys used to issue stablecoins.

Christopher Smith, founder of Quantus, says:

In the future, post-quantum cryptography will simply 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 placing a first practical attack toward the late 2020s. A “Quantum Doom Clock” created by two of its contributors points to March 2028 as the first possible window.

This date does not represent a scientific consensus. Other experts envision the 2030s instead, while the necessary advancements in error correction and logical qubit production remain considerable.

A Google study published in 2026 estimates that a machine with fewer than 500,000 physical qubits could, under certain assumptions, break the elliptic 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 adapted addresses. They would not automatically solve the cases of lost wallets, deceased owners, or holders who never move their bitcoins.

Proposal BIP-361 considers a gradual transition to new signatures, then a restriction of the old ones. It raises a sensitive question: should coins that do not migrate be frozen to prevent theft, at the risk of altering the rights attached to legitimately held bitcoins?

The Alliance will not be able to impose an answer on Bitcoin, whose rules evolve by consensus. Its usefulness will lie mainly in creating common tests and comparable migration methods. The threat remains theoretical, but the time needed for a worldwide upgrade justifies preparing this transition well before the arrival of a machine capable of attacking the keys.

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