Researchers at AmericanFortress have proposed a cryptographic system designed to protect Bitcoin and other blockchain wallets from future quantum computing attacks without requiring users to change their existing wallet addresses.

AmericanFortress, a Wyoming-based company specializing in blockchain security, post-quantum cryptography, and digital asset infrastructure, outlined its approach in a paper titled "ZKPoSP: Post-Quantum Zero-Knowledge Proofs for Hierarchical Deterministic Wallets." The system replaces traditional elliptic curve digital signatures with zero-knowledge proofs while maintaining full compatibility with the hierarchical deterministic wallet standards that underpin most modern cryptocurrency wallets.

The research centers on what experts call "Q-Day"—the anticipated moment when a fault-tolerant quantum computer becomes capable of running Shor's algorithm to derive private keys from public keys. Such a breakthrough would undermine the elliptic curve cryptography that secures Bitcoin and numerous other blockchains. While cryptographically relevant quantum computers do not yet exist, the U.S. National Institute of Standards and Technology finalized its first post-quantum cryptography standards in August 2024, signaling that governments and industry consider the threat serious enough to begin widespread preparation.

"Recent advances in quantum hardware, including Google's Willow processor, have substantially narrowed the timeline to cryptographically relevant quantum computers," the researchers wrote. "In the blockchain setting, where addresses and key derivation standards such as BIP32, BIP44, and SLIP-10 are the dominant infrastructure for wallet management, a quantum computer running Shor's algorithm can recover any elliptic-curve private key from the corresponding public key, threatening every wallet in production today."

Rather than forcing users to migrate funds to new quantum-resistant addresses, the proposed system substitutes digital signatures with zero-knowledge proofs that verify ownership of a wallet's seed phrase. Because the seed phrase itself remains secret, the authors argue that legitimate owners could still prove control of their wallets even if individual private keys are compromised by a quantum adversary.

The paper introduces two key components: ZKPoSP (Zero-Knowledge Proof of Seed Provenance) and QBIP32, a key derivation scheme engineered to support multiple elliptic curves while remaining compatible with existing hierarchical deterministic wallets. According to the study, the AmericanFortress team implemented the system in Rust using the RISC Zero zero-knowledge virtual machine. Prototype benchmarks showed proof generation times of approximately 12 to 13 seconds and verification times of about 9 to 10 milliseconds. The paper also details a post-Q-Day operating mode that reduces proving time for certain operations.

The research has not yet been adopted by any blockchain network. Any real-world deployment would require coordinated adoption across developers, wallet providers, exchanges, miners, and end users—a hurdle that has historically made even modest Bitcoin protocol changes, such as the years-long debate preceding SegWit activation in 2017, deeply contentious.

Bitcoin faces a particularly acute quantum vulnerability because spending coins exposes their public keys on-chain. A sufficiently powerful quantum computer could leverage those exposed public keys to derive private keys and forge valid transaction signatures.

This paper is the latest in a wave of industry initiatives aimed at preparing blockchain networks for a post-quantum future. Earlier this month, Project Eleven proposed a post-quantum recovery mechanism allowing users to prove Bitcoin wallet ownership through seed phrases rather than digital signatures after Q-Day. In March, BTQ Technologies released the first working implementation of BIP-360 on a dedicated "Bitcoin Quantum" testnet to evaluate quantum-resistant transaction formats.

In May, blockchain analytics firm Glassnode estimated that approximately 6.04 million Bitcoin—roughly 30% of the circulating supply—already have publicly exposed keys. That same month, the U.S. Department of Commerce announced more than $2 billion in funding for quantum computing companies and manufacturing initiatives.

Last week, major industry participants including BlackRock, Coinbase, Strategy, Fidelity Digital Assets, Galaxy, and others formed the Bitcoin Security Consortium, committing $15 million over three years to support Bitcoin security research and defense against quantum attacks.