StarkWare says the first Bitcoin mainnet transaction using its Quantum-Safe Bitcoin, or QSB, construction was successfully mined on August 26, demonstrating a hash-based protection method that works without changing Bitcoin’s consensus rules. Developed by StarkWare researcher Avihu Levy, with additional engineering work from Tomer Giladi, the experiment shows that selected Bitcoin outputs can be moved into a quantum-resistant construction using rules already accepted by the network. StarkWare’s announcement describes the event as QSB’s first mainnet execution.
The transaction was mined by MARA Pool after being submitted through MARA’s Slipstream service. QSB transactions currently use a nonstandard format that ordinary Bitcoin nodes will not relay through the public mempool, making direct miner submission necessary. The method therefore avoids a soft fork at the consensus level but still depends on specialized infrastructure to reach a miner under current relay policies.
QSB Replaces One Quantum-Sensitive Layer With Hash Security
Bitcoin normally relies on elliptic-curve signatures to authorize spending. A sufficiently capable future quantum computer running Shor’s algorithm could undermine the mathematical assumptions protecting exposed public keys. The U.S. National Institute of Standards and Technology similarly warns that cryptographically relevant quantum computers could break widely used public-key systems and has standardized new post-quantum algorithms based partly on hash functions. QSB addresses that specific threat by adding a spending condition whose security depends on hash resistance rather than elliptic-curve secrecy.
The construction uses a technique known as signature grinding. Before broadcasting, the sender performs substantial off-chain computation to find a transaction whose hash satisfies the required signing condition. StarkWare says the process currently costs several hundred dollars and draws heavily on the Binohash construction developed by Robin Linus. That computational expense is part of the trade-off for obtaining quantum-resistant spending without modifying Bitcoin’s existing consensus rules.
QSB also has an important limitation: it cannot retroactively protect coins whose public keys were already exposed before the protective transaction is broadcast. A future quantum attacker could theoretically derive the associated private key before those funds reach the new output. The method is therefore a migration mechanism for appropriately positioned coins, not a blanket quantum-security upgrade for every Bitcoin address.
Mainnet Test Does Not Make Bitcoin Quantum-Safe
The transaction can be inspected through mempool.space under transaction ID 305a24ffea912b9cf428f29ebf952321c96dab5bab284fc0d0801562f5abab07. It was confirmed in Bitcoin block 964,199. The long hexadecimal value is the transaction ID, not the block height, an important distinction when referencing the on-chain record.
StarkWare itself cautions that QSB does not make Bitcoin as a whole quantum-resistant. The company continues to argue that a protocol-level soft fork would provide a stronger long-term migration path, while QSB offers a voluntary mechanism that can operate before such consensus changes are adopted. The mainnet transaction is consequently a proof of practical feasibility rather than evidence that Bitcoin’s quantum-security problem has been resolved.
The demonstration arrives as Bitcoin developers and researchers explore multiple post-quantum approaches, including the separate SHRINCS proposal focused on compact signatures. QSB adds another option to that debate by showing that hash-based protection can already be exercised on mainnet, albeit with higher computational costs, nonstandard relay requirements and limited protection for previously exposed keys.