A freshly published white paper from Google’s Quantum AI team is stirring heated discussions surrounding the security of leading cryptocurrencies, including Bitcoin and Ethereum. The research suggests that the level of computational power required to breach the encryptions safeguarding these networks might be considerably less formidable than previously thought. Even though Bitcoin’s recent Taproot upgrade aimed to enhance its efficiency and privacy, it may inadvertently have made the network more susceptible to threats from quantum computing.
Are Quantum Breakthroughs Within Reach?
Google’s findings challenge earlier predictions about the number of quantum bits necessary for a quantum assault on Bitcoin’s cryptographic defenses. Initially, experts believed millions of qubits would be essential, which placed such a risk well in the future. Google’s scientists now propose this number could be less than half a million, hinting at a potentially shorter timeline for vulnerability. They describe hypothetical attack models requiring only between 1,200 and 1,450 high-quality qubits.
Previously, Google marked 2029 as the target year for achieving practical quantum systems. The updated insights present a scenario where risks to cryptocurrencies from quantum advances might materialize sooner than projected by most stakeholders in the field.
Will Transaction Timeliness Affect Vulnerability?
Yes, the study suggests attackers with access to a sufficiently fast quantum computer could exploit real-time transactions. When Bitcoin is transferred, the public key of the recipient momentarily becomes visible. During this brief exposure, a quantum computer could potentially compute the private key, thereby intercepting and redirecting the transaction before it is confirmed on the blockchain.
In simulations, Google calculated that pre-computation could help speed up the process. In a situation where a quantum-assisted attacker engages during a cryptocurrency transfer, they might finalize the exploit within approximately nine minutes. Given the typical ten-minute duration required for Bitcoin transactions to get confirmed, the chances of an attacker succeeding stand at roughly 41%.
Ethereum and similar networks that confirm transactions almost immediately might offer a reduced window for such quantum threats, potentially minimizing their exposure.
Notably, the study found around 6.9 million Bitcoins—or nearly a third of the total supply—reside in wallets where public keys have, at some point, been exposed. This includes nearly 1.7 million coins from Bitcoin’s inception and current assets stored in previously used addresses. Google’s insights suggest these wallets may be at greater risk than was previously acknowledged.
“Due to the Taproot design choice, the number of wallets potentially exposed to quantum-based attacks may increase,” the researchers concluded.
To mitigate potential misuse, Google’s quantum team chose not to disclose sensitive technical details, instead using zero-knowledge proofs to support their conclusions. This approach aims to secure the trustworthiness of their findings while limiting possibilities for malicious applications.
