Bitcoin has completed an experimental quantum-safe transaction through a construction developed by StarkWare, highlighting ongoing efforts to address the potential security risks posed by increasingly powerful quantum computers. The transaction was designed to demonstrate that Bitcoin could adopt a quantum-resistant transaction mechanism without requiring changes to the network’s underlying protocol.
StarkWare confirmed the experimental transaction and credited Avihu Mordechai Levy with developing the Quantum Safe Bitcoin, or QSB, transaction scheme. The work was carried out in collaboration with the MARA Foundation and Tomer Giladi, according to the information provided.
The QSB scheme is designed to provide quantum-resistant security for Bitcoin without modifying the Bitcoin protocol, while remaining compatible with the network’s existing legacy script constraints.
Scheme targets quantum computing risk
Quantum computing presents a potential long-term challenge for blockchain networks because algorithms such as Shor’s algorithm could undermine cryptographic systems that rely on mathematical problems considered difficult for conventional computers. Bitcoin‘s existing cryptographic architecture could therefore face security concerns if sufficiently capable quantum machines become available.
Levy presented the QSB transaction scheme on April 9, 2026, as an approach intended to address that potential threat. The construction is designed to remain secure even under the assumptions associated with Shor’s algorithm, while avoiding a requirement to change Bitcoin’s core protocol.
The development reflects a broader concern across blockchain networks about preparing for advances in computing technology before quantum systems become capable of attacking widely used cryptographic mechanisms.
StarkWare modifies existing proof-of-work construction
The StarkWare approach builds on a construction referred to as BINOHASH. The development modifies the component considered vulnerable to quantum attacks by replacing a signature-size-based proof-of-work puzzle with a hash-to-signature puzzle.
According to the technical description, the security of the revised mechanism relies on the preimage resistance of RIPEMD-160 rather than the security properties of the replaced component. This change is intended to reduce the scheme’s dependence on cryptographic assumptions that could become vulnerable to quantum algorithms.
The resulting construction is reported to provide approximately 118-bit second-preimage resistance under a Shor-based threat model. Under Grover’s algorithm, the estimated security level is roughly half of that figure. These estimates are intended to describe the computational difficulty of successfully compromising the construction under different quantum attack scenarios.
Designed to work within Bitcoin’s existing limits
A significant feature of the proposal is its compatibility with Bitcoin’s existing scripting limitations. The scheme reportedly fits within the legacy Bitcoin script framework, using no more than 201 opcodes and remaining within a 10,000-byte size constraint.
This compatibility could be important because protocol-level changes to Bitcoin generally require extensive technical review and broad ecosystem coordination. A mechanism that can operate within existing script restrictions could provide an alternative route for experimenting with quantum-resistant functionality without immediately requiring a network-wide protocol upgrade.
Quantum-safe Bitcoin, mined on mainnet, Today.
Designed by @avihu28 – the first ever quantum-safe Bitcoin transaction was built in collaboration with @MARAFoundation_ and our own @giladi_tom85141.
Every chain faces the same quantum deadline. Today we took a huge step to move…
— StarkWare 🥷 (@StarkWareLtd) August 26, 2026
The experimental transaction also demonstrates that the concept can move beyond theoretical research into a working proof of concept. The transaction was described as being mined on Bitcoin’s mainnet, providing a practical demonstration of the proposed mechanism under real network conditions.
Low-cost testing could support further research
The technical description estimates that the off-chain GPU cost associated with the scheme could be a few hundred dollars. While this figure represents an experimental implementation rather than a prediction of future production costs, relatively accessible computational requirements could make further testing easier for researchers and developers.
The reported mainnet demonstration provides evidence that quantum-safe transaction concepts can be tested within Bitcoin’s existing operational environment rather than remaining solely theoretical proposals.
The development does not mean Bitcoin has been fully upgraded to withstand all possible future quantum attacks. Instead, it represents an experimental step toward evaluating alternative cryptographic mechanisms before quantum computing reaches a level capable of threatening current blockchain security.
As quantum computing research advances, blockchain developers are increasingly examining ways to preserve transaction security against potential future attacks. StarkWare’s QSB construction adds another technical approach to that effort, with its focus on protocol compatibility, hash-based security assumptions, and practical implementation.
The report indicates that the successful experimental transaction could provide a foundation for additional research into quantum-safe Bitcoin transactions and the broader challenge of preparing decentralized networks for the next generation of computing technology.