As quantum computers inch closer to the power needed to break Bitcoin’s cryptography, one security firm is pitching a way to prove wallet ownership even after that “Q‑Day” arrives.
Project Eleven on Thursday published a cryptographic recovery proposal that aims to solve a core post‑quantum problem: once a quantum machine can derive an elliptic curve (ECC) private key from its public key, digital signatures stop being reliable proof of ownership. “After Q‑Day, once a quantum computer can derive an ECC private key from its public key, a valid signature no longer proves ownership,” Project Eleven CEO Alex Pruden wrote. In that scenario, both a quantum attacker and the legitimate owner could produce identical signatures, meaning a signature alone can’t tell you who really controls a wallet.
The company’s answer is to shift the proof from signatures to key derivation. Instead of relying on a signature from a compromised private key, users would prove they control the parent key (the seed/derivation source used to generate that address) without revealing it. Because a quantum adversary might be able to reconstruct an individual address’s private key, Project Eleven argues, it still cannot reconstruct the higher‑level parent key from which that private key was derived. That makes it possible to distinguish an actual owner from an attacker even after the address key has been exposed.
Technically, the work builds on a concept known as “signature lifting,” originally proposed by researchers Alon Sattath and Robert Wyborski, and uses zero‑knowledge proofs to validate possession of the derivation seed without revealing it. Project Eleven collaborated with Jim Posen, lead maintainer of the open‑source Binius zero‑knowledge proof system, and funded an implementation using Binius—software optimized for hash‑heavy cryptographic proof work.
The proposed mechanism is intended as a recovery fallback for users who fail to migrate funds to quantum‑safe addresses before Q‑Day — a practical concession, as Pruden admits, that not every wallet owner will act in time. “This gives them a fallback: prove ownership through derivation, not signature, even after that window closes,” he wrote.
The proposal arrives amid accelerated industry and government movement toward quantum resistance. In February, Bitcoin developers moved BIP‑360 into formal review as groundwork for future post‑quantum upgrades. In March, BTQ Technologies released a working implementation on a Bitcoin Quantum testnet to let developers experiment with migration mechanics and to underscore the difficulty of achieving network consensus on such a change. In June, Coinbase’s quantum advisory council warned that roughly 7 million BTC could eventually be vulnerable if owners don’t move funds to quantum‑safe addresses. That same month, U.S. President Donald Trump signed executive orders aimed at speeding the federal government’s transition to post‑quantum cryptography, adding policy momentum to the technical work.
Project Eleven’s proposal doesn’t prevent quantum theft before migration; instead, it offers a recovery path for those who miss the migration window. If adopted and implemented with the necessary tooling and community coordination, the approach could become an important safety net in a post‑quantum Bitcoin ecosystem.
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