G7 Warns Quantum Computers Pose Threat to Public-Key Cryptography

The Group of Seven (G7) cybersecurity working group has issued an urgent call to action for governments and companies to prepare for the threat posed by quantum computers. According to a report released on September 3, the G7 believes that technology capable of threatening existing public-key cryptography is advancing faster than expected.

Bitcoin and Ethereum are among the cryptocurrency networks that use public-key cryptography for transaction signatures and fund management, making them vulnerable to potential attacks from quantum computers. The G7 identified 'harvest now, decrypt later' attacks as a key risk, where an attacker secures encrypted data now and decrypts it later when quantum computers become sufficiently advanced.

The European Union has already presented a specific transition schedule for post-quantum cryptography, with plans to begin the transition by the end of 2026 and complete migration before 2030. Bitcoin is preparing for quantum computers through BIP-360, a soft-fork proposal that aims to reduce long-term quantum attack risks.

Ethereum is planning a broader upgrade, including validators' BLS signatures and KZG commitments, ECDSA account signatures, and zero-knowledge proofs at the application layer. However, one of the biggest obstacles in implementing post-quantum cryptography is cost, as widely used secp256k1-based ECDSA signatures are about 64 bytes, while post-quantum signature methods can require much larger data.