Post-quantum security: what founders should build for now

Almost every blockchain in use today relies on public-key cryptography that a large enough quantum computer could, in theory, break. That machine does not exist yet, and nobody can say with confidence when it will. But the risk has a long tail, and blockchains are unusually exposed to it.

Why blockchains are exposed

Data on a public chain is permanent and visible to everyone. An attacker does not need to break a key today. They can record public data now and try to break it later, an approach often called "harvest now, decrypt later". Funds held in addresses whose public keys are already visible are the most exposed.

Blockchains are also slow to upgrade. Changing the signature scheme of a major network requires broad agreement across developers, validators, exchanges and wallet providers. That process takes years, which is why the work needs to start well before the threat is real.

Why the clock starts now

TodayData is recordedPublic keys and transactions are visible and permanent.

Next yearsNetworks migrateUpgrading signatures needs broad agreement and takes time.

FutureOld keys at riskA large quantum computer could break today's cryptography.

What founders can build now

Migration tooling. Wallets and custody providers will need simple ways to move funds from older key types to quantum-resistant ones, without asking users to understand the cryptography.

Hybrid signatures. Schemes that combine a classical signature with a post-quantum one let networks add protection without abandoning what already works.

Key management. Post-quantum keys and signatures are larger, which affects storage, fees and hardware wallets. There is room for products that make that overhead invisible to the end user.

Audits and monitoring. Teams will want to know how much of their exposure sits in vulnerable addresses and contracts, and how to reduce it step by step.

Four areas open for founders

1Migration toolingMove funds to quantum-resistant keys in a few clicks.

2Hybrid signaturesAdd protection without dropping what works.

3Key managementHide the cost of larger keys and signatures.

4Audits and monitoringShow exposure and reduce it step by step.

Our view

Post-quantum security is one of the five areas in the Cequire thesis because the work is necessary, technically deep and still early. The teams that build the bridges now will be the ones the industry relies on when the timeline shortens.