StarkWare researcher unveils a way to make Bitcoin “quantum-safe” today — but it’s expensive and meant as an emergency fix
A StarkWare researcher, Avihu Levy, has published what he says is the first method to make Bitcoin transactions resistant to future quantum attacks on the live network without changing the Bitcoin protocol. The catch: the approach can cost between about $75 and $200 per transaction and is intended as a last-resort emergency tool rather than a permanent solution.
What QSB is and how it works
- Name: Quantum Safe Bitcoin (QSB).
- Core idea: Replace signature-based security assumptions with hash-based proofs to resist quantum attacks. Whereas today’s Bitcoin relies on ECDSA/ Schnorr signatures (which could be vulnerable if powerful quantum computers ever derive private keys from public keys), QSB substitutes those assumptions with hash-based constructs that are much harder to break even for quantum-capable machines.
- Practical tradeoff: The scheme preserves Bitcoin’s existing consensus rules for legacy transactions — no soft fork, no miner signaling and no protocol activation required. That means it can, in theory, be used on the live network today.
Why it’s expensive
- Security is shifted from consensus to brute-force computation. Generating a valid QSB transaction requires searching through billions of candidates — heavy off-chain GPU work.
- Levy estimates commodity cloud GPUs would make each protected transaction cost roughly $75–$200 to produce. For context, a typical Bitcoin transaction fee today is roughly $0.33.
- Because of that computational burden, QSB is explicitly pitched as an emergency workaround rather than a scalable long-term replacement for protocol changes.
How it compares to other proposals
- BIP-360 is a competing quantum-resistance approach that proposes protocol-level changes (a soft fork) to introduce quantum-resistant signatures. BIP-360 was added to Bitcoin’s improvement proposal repository in February but has no Bitcoin Core implementation and faces uncertain, multiyear governance timelines.
- QSB’s selling point is immediacy: it requires no protocol changes and could be used now. The downside is cost, complexity and practical limitations.
Practical limitations and tradeoffs
- QSB transactions are heavy to create and require outsized computation performed off-wallet (e.g., rented GPUs or specialized hardware).
- They won’t integrate with cheap, fast second-layer systems like Lightning, and they’re more complex than standard signing workflows.
- Levy suggests users will likely need to deliver QSB transactions directly to miners willing to include them, rather than relying on normal wallet-to-mempool broadcasts in user-friendly ways.
Context and final take
- Levy frames QSB as a “last resort measure” — useful if and when a quantum threat materializes before a protocol-level fix can be deployed. Protocol upgrades like BIP-360 remain the more elegant and scalable long-term solution but could take years to activate. Historically, major Bitcoin upgrades can be slow (for example, Taproot took around seven and a half years from idea to deployment).
- On the timeline for actual quantum danger: mature, general-purpose quantum machines that can break the widely used cryptography are not expected to appear immediately, but the risk is nonzero and motivates research like this.
Bottom line: QSB offers a technically feasible way to harden existing Bitcoin transactions against quantum attacks today without changing the protocol, but it comes at high per-transaction cost, operational complexity, and limited compatibility. It’s a potentially valuable emergency option — not a substitute for a coordinated, protocol-level upgrade to long-term quantum-resistant signatures.
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