A Bitcoin (BTC) transaction using Starkware researcher Avihu Levy’s quantum-safe Bitcoin QSB method has been confirmed on the Bitcoin mainnet. This marks the first reported mainnet demonstration of the experimental construction. The transaction was created to safeguard BTC from future attacks involving powerful quantum computers without needing a soft fork or changes to BTC’s consensus rules. Levy developed QSB as a way to move Bitcoin into an output protected by hash-based assumptions rather than depending on elliptic curve cryptography used by traditional BTC transactions. This approach is experimental, and its present computational requirements mean it is not yet a practical replacement for BTC’s present transaction system.A few months later – a Quantum Safe Bitcoin tx on mainnet: https://t.co/qbrXRYXTd6Thanks to StarkWare’s @giladi_tom85141 taking this to the finish line and @MARAFoundation_ Slipstream mining this non-standard txAlso @robin_linus & @Ethan_Heilman on previous work led to QSB https://t.co/cRHzUEOAIk— Avihu Levy (@avihu28) August 26, 2026QSB Moves Bitcoin’s Security Beyond Elliptic Curves Bitcoin’s existing signature system depends on elliptic curve cryptography, which could become susceptible to a capable quantum computer running Shor’s algorithm. A quantum attacker could potentially derive a private key from a publicly exposed BTC public key and use it to spend the associated funds. Most BTC addresses currently decrease this exposure by keeping the public key hidden behind a hash until the owner sends the coins. Once a transaction is broadcast, the public key becomes visible.This could create a chance for future quantum attackers to get the corresponding private key before the transactions are done. QSP attempts to address this issue by adding extra protection based on hash functions. The method uses signature grinding to produce a valid Bitcoin signature without depending on possession of a conventional private key. Sender performs the computational work off-chain and searches for a transaction whose hash satisfies the needed conditions.The outcome transaction can then be accepted by Bitcoin as it currently operates because the network itself does not need to recognize a new consensus rule. The first mainnet transaction depicts that the construction can work outside a research environment. According to the X post, the transaction was mined using MARA slipstream, which provided a path for the non-standard transaction to reach a miner. The method is still far from being a main Bitcoin transaction option. The QSP currently requires $75 to $150 in off-chain GPU computation per transaction and its non-standard transaction format also means that it does not follow the normal BTC mempool route and currently needs a direct mining path.First Mainnet Transaction Emphasizes Bitcoin’s Quantum Challenge The transaction represents a practical demonstration of a challenge that has largely remained a long-term problem for the BTC ecosystem. Levy published the QSB research in April 2026 and created the method as a personal project after being involved in the BTC system. StarkWare engineer Tomer Giladi later helped bring the work to a functioning mainnet transaction. Levy acknowledged the contribution of Giladi and MARA Slipstream following the transaction, while also crediting earlier work from Robin Linus and Ethan Heilman that contributed to the development of QSB. StarkWare CEO Eli Ben-Sasson has also argued that a Bitcoin soft fork remains the preferred long-term solution for quantum protection. However, the successful transaction depicts that users may have another way for protecting funds before such protocol-level change takes place. Development also comes as StarkWare continues working on quantum resistance elsewhere in its ecosystem.StarkWare’s broader technology uses ZK-STARKs, which depends on hash-based cryptographic assumptions rather than elliptic curves, although QSB itself does not use STARKs. The company, the organization, has separately outlined a multi-phase blueprint for improving quantum resistance on StarkNet. This effort involves rotating several parts of the network and eventually addressing dependencies connected to Ethereum’s base layer. For Bitcoin, the QSB transaction offers a distinct kind of demonstration: a quantum-resistant spending construction operating without modifying BTC’s consensus rulesThe significance of the transaction therefore expands beyond the small amount of Bitcoin involved. It shows that quantum-resistant Bitcoin spending has moved from a purely theoretical conversation towards an experimental implementation on the live network. Technology still needs to become less costlier, easier to use, and widely compatible before it can be chosen as a practical solution for ordinary Bitcoin holders