In a recent research note, Grayscale, a digital asset management firm, emphasized the need to expedite efforts to make public blockchains resistant to quantum computing threats. Although the necessary technical solutions are already available, the primary obstacle lies in securing agreement among decentralized communities to implement these changes. This comes on the heels of a paper by Google Quantum AI, which revealed that breaking Bitcoin's elliptic curve cryptography could be accomplished with fewer than 500,000 physical qubits, a substantial reduction from previous estimates, and could be executed in under nine minutes once the machine is prepared. Following the release of this paper, the industry has been abuzz with responses, including an analysis by CoinDesk that found an attacker would have approximately a 41% chance of stealing funds before a Bitcoin transaction is confirmed.
Grayscale's research highlighted four key takeaways from Google's findings, including the potential for progress toward a cryptographically relevant quantum computer to occur in discrete jumps, rendering timelines unpredictable. The technical solutions, specifically post-quantum cryptography, are mature and already securing certain blockchain transactions and internet traffic. Moreover, quantum risk varies significantly across different blockchains, depending on factors such as their transaction model, consensus mechanism, and block time. From a purely engineering perspective, Bitcoin is considered to have lower quantum risk compared to other chains due to its UTXO model, proof-of-work consensus, lack of native smart contracts, and specific address types that are not vulnerable to quantum attacks if not reused after spending.
However, the more challenging question revolves around the roughly 6.9 million BTC, including an estimated 1 million believed to belong to Satoshi Nakamoto, that are sitting in wallets with public keys already exposed on the blockchain. The options for addressing this issue include burning these coins, taking no action, or deliberately slowing their release by limiting the spending rate from vulnerable addresses. Grayscale noted that the Bitcoin community has a history of contentious debates over protocol changes, which could hinder the decision-making process. In contrast, Ethereum faces a distinct set of challenges, with Google's paper identifying five separate attack vectors worth over $100 billion in combined exposure.
An Ethereum Foundation researcher estimated a 10% chance of quantum key recovery by 2032, highlighting the need for timely action.