Security research firm Project Eleven has unveiled a cryptographic technique designed to let Bitcoin wallet owners prove they still control their funds even after a quantum computer breaks the elliptic curve cryptography securing those wallets, CEO Alex Pruden announced in a thread on X.
The Core Problem: Signatures Become Unreliable After Q-Day
‘Q-Day’ refers to the moment a sufficiently powerful quantum computer can derive a private key from a public key, rendering standard digital signatures useless as proof of ownership. Once that threshold is crossed, both a legitimate wallet owner and a quantum-equipped attacker can produce identical valid signatures.
Pruden framed the central challenge not as protecting wallets from quantum attacks, but as proving who owns them once those attacks become possible. As he put it: ‘a valid signature no longer proves ownership.’
How Project Eleven’s Technique Works
The proposed solution exploits a structural property of Bitcoin’s hierarchical deterministic wallets. Every wallet address is derived from a parent key via a key derivation path. Project Eleven’s approach lets a user generate a cryptographic proof that they know and control that parent key, without ever revealing it publicly.
Because a quantum computer cannot reconstruct the parent key or seed phrase from a compromised child private key, this derivation proof distinguishes a legitimate owner from an attacker who has merely cracked the exposed address key. As Pruden described it, proving you know that parent key without revealing it is something only the real owner can do, even after Q-Day.
Technical Foundation and Collaborators
The implementation was built in collaboration with Jim Posen, lead maintainer of the open-source Binius zero-knowledge proof system. Project Eleven funded Posen to apply the Binius system, which is designed to accelerate hash-heavy cryptographic operations, to this problem.
The approach builds on a technique called ‘signature lifting,’ first proposed by academic researchers Alon Sattath and Robert Wyborski. Project Eleven stressed that the current prototype is unaudited and would require formal blockchain protocol support before it could be deployed in practice.
A Fallback for Those Who Miss the Migration Window
The mechanism is explicitly designed as a safety net for users who do not move their funds to quantum-safe addresses before a future network-wide migration deadline.
‘As much as I would love for the entire world to take a quantum migration plan seriously, the reality is that some digital asset wallets will miss the window,’ Pruden wrote. ‘This gives them a fallback: prove ownership through derivation, not signature, even after that window closes.’
Broader Context: Bitcoin’s Quantum Preparation Accelerates
- In February 2026, Bitcoin developers moved BIP-360, a quantum-resistant upgrade proposal, into formal review.
- In March 2026, BTQ Technologies released the first working implementation on a Bitcoin Quantum testnet.
- In June 2026, Coinbase’s quantum advisory council warned that roughly 7 million Bitcoin could be vulnerable if owners fail to migrate to quantum-safe addresses.
- Also in June 2026, President Donald Trump signed executive orders accelerating the federal government’s transition to post-quantum cryptography.
Project Eleven’s recovery proposal adds a distinct layer to these preparations: not prevention, but a credible ownership-verification fallback for wallets that are already compromised at the signature level.
