Google has warned that elliptic curve cryptography used in many cryptocurrency wallets may be vulnerable to quantum attacks within a shortened timeframe. The company estimated that compromising ECC-256 could require fewer than 500 000 qubits and take only minutes.

Google's assessment

According to Google, this finding lowers prior resource estimates and shifts the projected window for practical quantum attacks closer, to about 2029. ECC-256 is a common public-key algorithm underlying private-key generation and transaction signatures in many blockchain networks and cryptocurrency wallets.

Potential impact

Google noted that millions of bitcoins could be exposed if attackers obtain sufficient quantum resources. Old and dormant addresses that rely on ECC-based keys are especially vulnerable because their public keys or past signatures may already be visible on-chain.

Technical context

The company specified a threshold of fewer than 500 000 qubits for an effective attack on ECC-256. It added that such an operation could complete in minutes rather than years, a change that shortens the horizon for when the threat becomes practical.

In elliptic curve systems, public keys or transaction signatures exposed on the blockchain can enable private-key recovery if quantum algorithms reach the required scale, allowing potential unauthorized transfers of funds.

Implications for the ecosystem

The announcement highlights the need for industry consideration of post-quantum cryptography and improved key-management practices. The security community has long discussed migration paths to quantum-resistant algorithms, and this assessment may intensify those discussions across cryptocurrency projects and custodians.

Google made the assessment public as part of its research findings, reducing previous resource assumptions and establishing a nearer-term timeframe for quantum threats around 2029.