The First Quantum-Resistant Bitcoin Transaction Has Been Mined

A StarkWare researcher has successfully sent the first Bitcoin transaction designed to resist attacks from a sufficiently powerful quantum computer. The experimental transaction landed on Bitcoin’s mainnet without requiring a soft fork or any change to the network’s consensus rules.

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While the achievement is significant, it is not a full fix for Bitcoin’s potential quantum problem. It is better understood as a demonstration that users can create a quantum-resistant escape hatch today, even while developers continue debating a permanent protocol-level solution.

Quantum computers pose a potentially serious problem for Bitcoin because much of the network’s security depends on cryptographic assumptions that powerful enough machines could eventually defeat. Bitcoin uses elliptic-curve cryptography for the signatures that prove ownership of coins. A cryptographically-relevant quantum computer running Shor’s algorithm could theoretically derive a private key from an exposed public key, allowing an attacker to spend funds they do not own.

The biggest practical concern is the bitcoin already sitting in addresses that could eventually be vulnerable to a quantum attack. Glassnode estimated in May that roughly 6.04 million BTC, or 30.2% of the issued supply, had public keys exposed on-chain. At a bitcoin price of $80,000, that translates to roughly $483 billion worth of potentially vulnerable coins.

That huge pool of potentially stealable bitcoin is why the issue has sometimes been described as a quantum treasure hunt. Bitcoin creator Satoshi Nakamoto’s early coins alone, which may otherwise never move if it turns out no one has the associated keys, represent an extraordinary potential prize for whoever develops a sufficiently powerful quantum computer.

Some Bitcoin developers have spent much of the past year arguing over what should happen before such a machine arrives. The emerging view is less about rushing an emergency change into Bitcoin today and more about having a migration mechanism ready to deploy before so-called Q-day, the point at which quantum computers become capable of breaking Bitcoin’s existing signatures.

Matt Corallo, who was one of the earliest developers to work on Bitcoin, has argued that the immediate objective should be increasing the number of coins that can be secured before a cryptographically relevant quantum computer exists. In a Bitcoin developer discussion this year, he wrote that the community should seek to “minimize the chance that the Bitcoin community feels the need to fork to burn coins” by reducing the amount of bitcoin that remains vulnerable.

Corallo has also described a future in which a soft fork could disable vulnerable spending paths once the threat becomes sufficiently serious. The precise mechanism remains controversial, particularly over what should happen to coins whose owners fail to migrate. Should those coins be frozen forever at some point or should an entity with a quantum computer be able to snatch them up?

The issue has attracted attention well beyond Bitcoin’s core developer community. Coinbase established an independent advisory board focused on quantum computing and blockchain security in the crypto space at large. In July, Coinbase, Strategy, BlackRock, Galaxy, Fidelity Digital Assets, Blockstream and other companies founded a consortium that pledged $15 million over three years toward Bitcoin security research, with post-quantum cryptography as its first focus.

People need to stop giving this guy's FUD the time of day.

Literally *the* top two Bitcoin research orgs (Blockstream Research and Chaincode) have each put resources into figuring out what a post-quantum Bitcoin change should look like, and have had some interesting results!… https://t.co/AyldCEH0by

— Matt Corallo