On July 15, Project Eleven, a company specializing in post-quantum cryptography, presented an early prototype of a zero-knowledge proof (ZK-proof). This mechanism could potentially solve one of the most acute problems of Bitcoin's future: how to prove ownership of a wallet when a quantum computer can forge any digital signature.
The idea is elegant but complex. Instead of simply proving knowledge of the current private key (which a quantum attacker might have already recovered), the user proves control over an earlier, parent key in the hierarchical structure of an HD wallet. This parent key is protected by a derivation step using HMAC-SHA512 — a hash function whose resistance to quantum attacks (Grover's algorithm) remains at an acceptable security level.
How the "quantum insurance" works
It is based on the "signature lifting" method described by researchers in 2023. After "Q-day" — the moment when a quantum computer can recover a private key from a public one — a regular signature ceases to be proof of ownership. The proposed ZK-protocol allows replacing this signature with a post-quantum proof, using the same key pair but relying on a one-way function resistant to quantum cracking.
The prototype, developed jointly with Binius lead developer Jim Posen, has already demonstrated impressive performance. On a MacBook Air with an M5 chip, proof generation took 243 ms, the full cycle about 910 ms, and verification just 40 ms. Peak memory consumption was 2.1 GB, and the proof size was 358 KiB. Currently, the prototype supports three address types: P2PKH, P2WPKH, and P2SH-P2WPKH. Taproot support is not yet implemented.
The path from prototype to reality
It is important to understand that this is only an early, unaudited implementation. It does not work on the Bitcoin mainnet. Its deployment would require either a change in consensus rules via a soft fork or the creation of a separate verification system. The community will have to resolve difficult questions: when to stop accepting regular signatures for vulnerable addresses and how to resolve conflicts between a legitimate owner and an attacker who has already withdrawn funds.
This development is not a panacea, but rather a safety mechanism for those who fail to migrate to the post-quantum era in time. It complements, rather than replaces, more fundamental proposals such as BIP-360 (P2MR), which is already included in the official Bitcoin Improvement Proposals repository. I recall that in June, the Coinbase Quantum Advisory Council estimated that approximately 7 million BTC are potentially at risk due to old outputs and address reuse.
My analysis: Project Eleven demonstrates a technically mature and pragmatic approach to one of the most complex problems in cryptography. However, the key challenge remains not technical, but socio-political: can the Bitcoin community reach consensus on such an update quickly enough to outpace the quantum threat? Time is the most scarce resource in this race.