Avihu Levy, chief product officer at StarkWare, has proposed a cryptocurrency plan that he claims will make Bitcoin transactions secure for today’s quantum computing — without the need for a soft fork, a hard fork, or any modification to the existing protocol.
It was published on Thursday on GitHub, Quantum Secure Bitcoin (QSB) proposal. It operates entirely within the constraints of Bitcoin’s legacy script, and is designed to remain secure, Levy says, even against an adversary running Shor’s algorithm on a large-scale quantum computer.
The catch is big: Each transaction will cost the sender between $75 and $150 in GPU computation, making the scheme impractical for routine use and limiting its relevance, at least initially, for large-value transfers.
Quantitatively secure Bitcoin transactions without soft forkshttps://t.co/1lx5waX9VV pic.twitter.com/Ni7pA6dEsC
– Avihu Levy ✨🐺 (@avihu28) April 9, 2026
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The Hash-to-Sig Puzzle Mechanism: What Does the Proposed Bitcoin Quantum Scheme Actually Do
Bitcoin’s current signature system—the Elliptic Curve Digital Signature Algorithm, or ECDSA—derives its security from the computational robustness of the discrete logarithm of the elliptic curve problem. This rigidity does not withstand a sufficiently powerful quantum computer using Shor’s algorithm, which can solve the problem in polynomial time.
like Recent research from Google Quantum AI Although it is becoming increasingly tangible, the hardware threshold for carrying out such an attack may be closer than previously designed – with estimates suggesting that ECDLP-256 could be cracked using approximately 500,000 physical qubits, a 20-fold compression of previous expectations.
Levy’s proposal avoids ECDSA entirely by replacing the signature-volume proof-of-work puzzle with what he calls the signature hash puzzle.
Instead of proving knowledge of the private key through elliptic curve calculations, the spender must find an input whose hash output randomly resembles a valid ECDSA signature — an aggressive search task that offers no shortcut to quantum computing algorithms. In other words, the security model shifts from mathematical structure, which Shor’s algorithm can exploit, to resistance to prior image hashing, which it cannot.
More computing power is required for QSB. source: github
Main implication: QSB does not correct ECDSA – it replaces the cryptographic assumption behind the spend state, while leaving Bitcoin’s transaction format, consensus rules, and text engine unchanged.
QSB Proposal: Claims, Methodology, and What Has Not Been Verified Yet
Levy’s proposal, which has not been peer-reviewed or formally published through an academic venue at the time of writing, outlines the creation of a transaction that encrypts a hash-to-signature puzzle within existing Bitcoin text fundamentals. No new operating codes are needed.
There is no need to coordinate miners. From the network’s point of view, a QSB transaction is indistinguishable from a legacy transaction – it simply spends an output using a scriptSig that meets an unusually generated scriptPubKey.
The computational burden falls entirely on the sender. Finding a prior hash image that mimics a valid ECDSA signature requires very powerful GPU work — Levy estimates $75 to $150 per transaction at current computing prices. These cost figures are not relevant to, for example, moving cold storage at the cabinet level; It is forbidden to drink coffee. Levy acknowledges this directly, framing QSB as a stopping point for large BTC positions while the community deliberates on a long-term, protocol-wide solution.
This is huge. Bitcoin is quantum safe today.
Even if a quantum computer emerges, one that breaks traditional Bitcion signatures, it shows a practical way to create secure Bitcoin transactions. With no change in the Bitcoin protocol!!! https://t.co/ireGc3ai7W
– Eli Ben Sasson | Starknet.io (@EliBenSasson) April 9, 2026
Stark ware CEO Elie Ben-Sasson described the proposal in stark terms regarding X, noting that it “makes Bitcoin quantum safe today.” This framing does a great job of arguing — the scheme makes specific cryptographic transactions of great value to quantum computing resistant under its specific threat model, which is not equivalent to the Bitcoin network becoming quantum secure in any comprehensive sense. The proposal has not been independently verified, and no proposal to improve Bitcoin has been made to formalize or standardize the approach.
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Daniel Francis is a technical writer and Web3 educator specializing in macroeconomics and DeFi mechanics. A crypto native since 2017, Daniel brings his background in cross-chain analytics to author evidence-based reports and detailed guides. It is certified by the Blockchain Council and is dedicated to providing “information gain” that cuts through the market noise to find blockchain’s real-world utility.
