Circle has released a whitepaper detailing how its upcoming Arc blockchain will counter quantum computing threats. The roadmap, backed by institutional giants BlackRock, Visa, and Mastercard, consists of four phases, starting with opt-in post-quantum signatures at mainnet launch and culminating in full validator upgrades by 2030.
Arc is Circle's Layer-1 blockchain, designed to be EVM-compatible. Its public testnet debuted in October 2025, with mainnet planned for 2026. USDC, Circle's stablecoin, will serve as the native gas token. The network has demonstrated sub-second finality on testnet, far faster than Ethereum's roughly 12-minute finality.
The urgency stems from the 'harvest now, decrypt later' threat: adversaries could store encrypted data today and decrypt it once quantum computers mature. Experts predict a viable quantum computer could break current cryptography by 2030.
Phase one offers opt-in post-quantum signatures using NIST-standard lattice-based algorithms at mainnet launch. Phase two focuses on quantum-resistant private-state protection for smart contract data. Phase three hardens infrastructure, including communication and key management systems. Phase four, by 2030, upgrades the validator and consensus layer. A trade-off: post-quantum signatures could increase transaction sizes 2 to 10 times.
The backing from BlackRock, Visa, and Mastercard signals institutional-grade design. Circle aligns its timeline with regulatory expectations for quantum-proof financial infrastructure.
For investors, the 'harvest now, decrypt later' risk means current vulnerable transactions could be compromised. Ethereum has acknowledged quantum risks but lacks a concrete upgrade timeline. Potential bottlenecks from larger transaction sizes and a 2030 completion date leave a partial protection window.