The G7's cybersecurity working group has called on nations and enterprises to begin transitioning to post-quantum cryptography immediately, warning that cryptocurrency networks, exchanges, and custodians must upgrade their systems before quantum computers can threaten current encryption methods.
In a September 3, 2026 report titled "Preparing for the Post-Quantum Era: A Call to Action," the working group identified quantum computing as a cybersecurity risk requiring advance preparation. Though the report does not mention cryptocurrency specifically, the implications directly affect blockchain technology, which relies on public-key cryptography for transaction security and fund management.
The "Harvest Now, Decrypt Later" Risk
A primary concern outlined in the report involves gathering encrypted data today for decryption once quantum technology becomes capable enough. Blockchain systems present a particular vulnerability: public keys and transaction history remain permanently visible on the ledger, leaving them exposed to future compromise.
The G7 recommends action across awareness campaigns, national policies, research funding, public-private collaboration, and post-quantum procurement requirements.
Europe Sets Implementation Deadlines
The European Union has moved beyond recommendations to concrete timelines. The EU implemented the Coordinated Implementation Roadmap for the Transition to Post-Quantum Cryptography in June 2025, requiring member states to begin transition by the end of 2026, with high-risk systems migrating immediately and completing by 2030.
As post-quantum requirements become embedded in procurement and cybersecurity regulations, companies without migration plans face potential compliance and competitive challenges.
Different Approaches for Major Blockchains
Bitcoin is exploring BIP-360, a soft-fork proposal aimed at reducing long-term quantum vulnerability by removing the Taproot key-path spend mechanism, though developers acknowledge that faster attacks on mempool transactions would still require post-quantum digital signatures. No activation date has been set.
Ethereum is pursuing a broader post-quantum framework. According to Vitalik Buterin's February 2026 roadmap, the network plans to upgrade four components: BLS validator signatures, KZG commitments, ECDSA account signatures, and application-layer zero-knowledge proofs. Ethereum targets core post-quantum infrastructure completion by 2029, though full migration may extend beyond that timeline.
Technical and Economic Challenges
The transition carries substantial technical costs. Post-quantum signature schemes are significantly larger than current standards—the compact secp256k1 ECDSA signature is approximately 64 bytes, while the ML-DSA-87 standard finalized by NIST uses about 4,627 bytes. These larger signatures increase storage, bandwidth, and transaction costs across networks.
In March 2026, Google Quantum AI published research indicating that breaking 256-bit elliptic-curve cryptography would require fewer resources than previously estimated. Google announced completion of its own system migration by 2029.
NIST has recommended phasing out 112-bit ECDSA after 2030 and forbidding its use after 2035.
Near-Term Migration Risks
The immediate market risk lies not in quantum computers breaking current encryption but in the migration process itself—governance disputes over protocol changes, development delays, larger transaction sizes, infrastructure modifications, and the exposure of public keys from older wallets already on public ledgers.
