Here’s a problem that most crypto projects aren’t talking about yet: quantum computers will eventually be powerful enough to break the cryptographic locks that secure every existing blockchain. Circle, the company behind it $USDCapparently doesn’t want to be overwhelmed.
The stablecoin giant has published a whitepaper outlining a phased post-quantum security roadmap for Arc, its upcoming Layer-1 blockchain. The plan includes everything from wallets and validators to off-chain infrastructure, with post-quantum signature support available when Arc’s mainnet goes live in 2026.
What Circle is actually building
The blockchain will feature NIST standard lattice-based algorithms, including ML-DSA, CRYSTALS-Dilithium and Falcon. These are cryptographic signature systems specifically designed to resist attacks from quantum computers, vetted by the US National Institute of Standards and Technology.
$USDC serves as the original gas token for Arc. Arc’s public testnet launched in October 2025. The mainnet target is sometime in 2026, and post-quantum signatures will be live from the very first block.
The roadmap doesn’t stop at launch either. Near-term plans include quantum-proof private state and confidentiality functions.
The ‘harvest now, declutter later’ problem
The roadmap specifically focuses on harvest-now-decrypt-later attacks. Today, adversaries can capture encrypted data, store it, and wait for quantum computers to become powerful enough to break it open.
Expert estimates suggest that Q-Day, the moment when quantum computers can break current public-key cryptography, could come as early as 2030.
Circle’s previous research on quantum readiness dates back to January 2026, indicating that the company had been working on this problem for months before publishing the Arc roadmap.
Why this matters to investors
Most existing Layer-1 blockchains will need to adapt quantum resistance through hard forks and protocol upgrades. Ethereum’s roadmap includes quantum resistance as a long-term goal, but competes with a backlog in scale upgrades.
Institutions that must comply with evolving cybersecurity regulations, especially in the US where NIST standards carry regulatory weight, may find Arc’s compliance with those exact standards compelling.
Post-quantum cryptographic signatures are significantly larger than their classical counterparts, which poses real challenges in terms of block size, transaction throughput and storage costs. Circle has not publicly detailed how Arc plans to manage these trade-offs at scale.