Circle’s Layer-1 blockchain Arc will launch with a post-quantum signature scheme baked into its architecture, positioning itself as one of the first networks designed from the ground up to withstand quantum computing threats. The feature, which Arc detailed in a blog post on Sunday, allows users to create quantum-resistant wallets from day one of mainnet, expected sometime in 2026.

The approach is deliberately opt-in. There is no forced migration, no disruptive network-wide reset, and no assumption that every wallet or software stack will support the new scheme immediately. That flexibility is designed to let the ecosystem transition at its own pace while ensuring early adopters can protect their assets now.

This story is an excerpt from the Unchained Daily newsletter.

Arc’s roadmap extends quantum resistance in phases. Near-term work focuses on protecting confidential transactions and private balances. The mid-term phase targets infrastructure hardening, aligning with broader industry transitions in TLS 1.3 and hardware security module protocols that already support post-quantum algorithms. Long-term, the plan covers validator authentication, which requires careful integration because post-quantum signatures can be an order of magnitude larger than current ones.

The timeline matters because some cryptographers estimate that “Q-Day,” the moment a sufficiently powerful quantum computer can break existing public-key encryption, could arrive by 2030. A related concern is the “harvest now, decrypt later” strategy, in which adversaries collect encrypted data today to crack later. For institutions managing long-lived digital assets, waiting to address the threat could mean the damage is already done before defenses are in place.