Project Eleven unveils post-quantum Bitcoin wallet ownership proof for Q-Day

Project Eleven has introduced a post-quantum cryptographic proof aimed at a key Bitcoin security problem that could emerge on "Q-Day," when quantum computers become capable of breaking the elliptic curve cryptography behind Bitcoin signatures. The technique is designed to let users prove they still control a wallet even after a quantum attacker can derive a private key and generate a valid signature, a scenario in which signatures alone would no longer reliably show ownership. The approach relies on a wallet's key derivation path, letting a user prove control of the parent key used to generate a wallet's private key without revealing that parent key itself. Project Eleven says that distinction matters because a quantum attacker who compromises an address's private key still would not possess the seed phrase or parent key from which it was derived. CEO Alex Pruden said the work was developed in collaboration with Jim Posen, lead maintainer of the open-source Binius zero-knowledge proof system, and builds on "signature lifting," a technique first proposed by researchers Alon Sattath and Robert Wyborski. The proposed recovery mechanism is intended for wallet holders who fail to migrate to quantum-safe addresses in time. The release comes as post-quantum planning in Bitcoin gathers pace: BIP-360 entered formal review in February, BTQ Technologies published a working implementation on its Bitcoin Quantum testnet in March, and Coinbase's quantum advisory council warned in June that roughly 7 million Bitcoin could eventually be exposed if owners do not move funds. Later that month, President Donald Trump signed executive orders to accelerate the federal government's shift to post-quantum cryptography.