Quantum Safe Bitcoin: StarkWare CPO Avihu Levy Proposes QSB

StarkWare CPO Avihu Levy has published a paper proposing Quantum Safe Bitcoin, or QSB, a way to make Bitcoin transactions more resistant to future quantum-computing attacks without changing Bitcoin’s base protocol. The proposal is still early, but it gives the Bitcoin community a concrete design to review instead of a vague warning about quantum risk.

What Avihu Levy Proposed With Quantum Safe Bitcoin

StarkWare’s About page lists Avihu Levy as the company’s CPO. Levy is also the author of Quantum-Safe Bitcoin Transactions Without Softforks, the paper that introduces the QSB idea for Bitcoin.

In the paper’s abstract, Levy says QSB needs no changes to the Bitcoin protocol. The same abstract says the scheme fits inside Bitcoin’s legacy script limits of 201 opcodes and 10,000 bytes, which matters because proposals that fit current rules are easier to test than changes that need a network-wide upgrade.

The project’s README says QSB targets about 118-bit second pre-image resistance under the Shor threat model. In simple terms, that is a claim about how hard it should be for an attacker to force a matching transaction digest, with the README estimating an off-chain search cost of about $75-$150.

Independent coverage from The Defiant says the design uses existing Bitcoin consensus rules and does not require a softfork, protocol upgrade, or community-wide coordination. That framing is the main reason the paper stands out from many older quantum-safety discussions around Bitcoin.

Why Quantum-Safe Ideas Matter for Bitcoin

“Quantum safe” here means trying to protect Bitcoin transactions against a future class of computers that could break some of today’s cryptographic assumptions. For regular holders, the appeal is simple: a design that works under current Bitcoin rules could, in theory, be tested sooner than a change that requires the whole network to upgrade.

A practical hurdle remains. Bitcoin.com reported that QSB transactions are described as consensus-valid but non-standard, which means they would likely need miner-direct submission rather than normal wallet-to-mempool relay.

That makes QSB more of a research path than a wallet feature today. The same gap between protocol possibility and everyday usability also shows up in Coinlineup’s coverage of the Bitcoin Lightning Network’s long rollout, miner-side network changes, and wallet-security tools.

That is also why the “no softfork” detail matters so much. Because QSB is framed around legacy-script compatibility and no community-wide coordination, the proposal lands as a practical infrastructure discussion instead of a purely theoretical warning.

What QSB Could Mean for Bitcoin If the Proposal Gains Traction

The most important caution is that QSB is not a deployed Bitcoin upgrade. The project README says a real pinning hit was found at sequence=151205 and locktime=656535577 after about six hours on eight GPUs, but the same README also says digest search and transaction broadcast are still pending.

Because the pinning hit result exists while the broadcast step remains pending, this story sits between a paper-only concept and a live-network rollout. There is evidence of working search results, but there is still no completed end-to-end transaction that everyday users can inspect on chain.

Levy also says in the paper that, to the best of the author’s knowledge, QSB is the first scheme to support quantum-safe Bitcoin transactions on the live network without consensus changes. That remains an author-asserted novelty claim rather than an independently proven industry fact.

The Defiant reported on April 9, 2026 that the GitHub release had gone public, which is why this matters now. Bitcoin does not have a settled quantum plan, but it now has a detailed proposal with named constraints, cost estimates, and an implementation trail the community can test, criticize, or ignore.

For regular holders, the takeaway is narrower than the headline. QSB does not change how you store or send BTC today, but it does move the quantum-safety debate closer to the broader network-health conversations behind on-chain activity and other long-term Bitcoin signals.

Disclaimer: This article is for informational purposes only and does not constitute financial or investment advice. Cryptocurrency and digital asset markets carry significant risk. Always do your own research before making decisions.