A panel at a recent Ethereum developer conference examined the quantum computing threat to Bitcoin, focusing on its signature system. Co-authors of BIP 360 stated that Bitcoin’s elliptic curve signatures are the primary risk, with about 30% of the total supply—over 6.9 million coins—sitting in addresses with exposed public keys. They noted that while breaking Bitcoin’s hashing algorithm would require impossibly large quantum hardware, recent advances are lowering the threshold to break its signatures, prompting increased planning across the crypto industry.
Quantum computing poses a specific threat to Bitcoin’s cryptographic foundations. According to Hunter Beast, co-author of BIP 360, signatures are the main vulnerability, not the SHA-256 hashing algorithm.
“Hash algorithms like SHA-256 are actually believed to be very difficult for even the most ideal, biggest quantum computer we can imagine,” Beast said. The concern lies with Shor’s algorithm, which could reverse-engineer private keys from public keys.
Alex Pruden of Project Eleven explained the consequence of this capability. “Ownership in Bitcoin is entirely conferred by your ability to sign a digital signature,” he stated.
Pruden pointed to a key technical milestone by Google in late 2024. The company’s Willow quantum computer demonstrated below-threshold error correction, proving the technology can scale.
Recent research has significantly lowered hardware estimates for breaking Bitcoin’s cryptography. Whereas 2021 projections required millions of qubits, a study last week suggested it could fall to around 100,000.
Project Eleven tracks vulnerable assets on its Bitcoin Risq List. The data shows over 6.9 million total coins are in addresses with exposed public keys.
Isabel Foxen Duke, co-author of BIP 360, said the challenge extends beyond cryptography to network politics. Migrating old coins, including those potentially owned by Satoshi Nakamoto, would require difficult consensus.
“If 4 million Bitcoin hit the market in a matter of hours once a quantum computer arises… that’s a potentially Bitcoin‑project‑destroying event,” Foxen Duke warned. The broader industry is now ramping up quantum preparations.
