StarkWare Mines Quantum-Safe Bitcoin Transaction on Mainnet
Bitcoin has taken another step in the long-running effort to prepare for potential quantum-computing threats.
On Aug. 26, a Bitcoin transaction using researcher Avihu Levy’s Quantum-Safe Bitcoin (QSB) construction was mined on the Bitcoin mainnet. StarkWare described the experiment as the first post-quantum-resistant Bitcoin transaction executed under the network’s existing consensus rules.
The demonstration is significant because it did not require a Bitcoin soft fork, hard fork or core protocol upgrade. Instead, QSB provides an opt-in method that can be used under Bitcoin’s current rules.
However, the experiment should not be mistaken for a network-wide quantum upgrade. QSB remains an early construction, comes with substantial computational costs and requires users to move funds into the protected system before they can benefit from its quantum-resistant properties.
Bitcoin Tests Quantum-Resistant Spending Without a Fork
The transaction demonstrated that a quantum-resistant spending mechanism can operate within Bitcoin’s existing consensus framework.
According to the mined transaction on Mempool, the test spent a 10,000-satoshi output on Bitcoin mainnet.
StarkWare said the transaction was submitted using QSB, a construction developed by Levy. Starknet Foundation Vice President of Growth Damo described the experiment as requiring no soft fork, hard fork or Bitcoin protocol upgrade.
Because the transaction used a nonstandard format, it would not normally propagate through Bitcoin’s public mempool. It was instead mined through MARA Foundation’s Slipstream service.
The test therefore demonstrates something specific: an individual can potentially use a quantum-resistant spending construction without waiting for the Bitcoin network to adopt new consensus rules.
Why Quantum Computing Matters for Bitcoin
Bitcoin currently relies on elliptic-curve cryptography to establish control over funds. Digital signatures allow users to prove that they possess the private keys required to spend bitcoin without revealing those private keys.
The concern surrounding quantum computing comes from Shor’s algorithm. A sufficiently powerful quantum computer could theoretically use the algorithm to solve mathematical problems that underpin widely used public-key cryptography.
For Bitcoin, the potential threat becomes particularly relevant when a public key is exposed. An attacker with a sufficiently capable quantum computer could theoretically derive the corresponding private key and create a fraudulent transaction.
For users looking to understand the basics of Bitcoin transactions and signatures, Bitcoin.com’s Bitcoin transaction guide provides background on how the existing system works.
The potential quantum threat is still theoretical at the required scale, but researchers and developers have increasingly explored ways to prepare Bitcoin before such computing capabilities become practical.
How QSB Approaches the Problem
QSB takes a different approach from Bitcoin’s existing signature system.
Rather than depending on elliptic-curve signatures, Levy’s construction uses a quantum-resistant spending condition based on hash functions. It also incorporates a technique known as signature grinding.
The approach moves much of the computational burden away from the transaction itself. Work can be performed offchain before the transaction is ultimately submitted to Bitcoin.
That trade-off comes with a cost.
The mainnet demonstration reportedly required hours of GPU computation and cost approximately $150 to $200. This makes the system considerably more expensive and cumbersome than ordinary Bitcoin transactions.
Levy initially published the QSB research in April. StarkWare engineer Tomer Giladi subsequently helped turn the construction into a working mainnet transaction.
Levy also credited earlier research from BitVM creator Robin Linus and researcher Ethan Heilman.
The Mainnet Test Does Not Make All Bitcoin Quantum-Safe
The most important limitation is that QSB is an opt-in solution.
Simply mining a quantum-resistant transaction does not change Bitcoin’s existing cryptographic security model. Users must deliberately move funds into the protected construction if they want to use it.
That means QSB cannot automatically protect every bitcoin held on the network.
It also cannot recover funds that have already been stolen or protect coins that become vulnerable before their owners migrate them. A future quantum attacker would still potentially be able to target funds whose cryptographic exposure leaves them susceptible.
For that reason, the demonstration should be viewed as a proof of concept and an additional option rather than a complete solution for Bitcoin’s quantum-security problem.
StarkWare Still Supports a Bitcoin Soft Fork
Despite demonstrating that QSB can operate without changing Bitcoin’s rules, StarkWare leadership continues to support a broader protocol-level solution.
StarkWare CEO Eli Ben-Sasson said he still expects Bitcoin to eventually adopt a soft fork for quantum resistance.
The distinction is important. A protocol-level upgrade could provide a standardized mechanism across the network, whereas QSB currently gives individual users an opt-in path.
The successful transaction therefore serves two purposes. It demonstrates that quantum-resistant spending can be constructed within Bitcoin’s existing framework, while also strengthening the argument that the network has practical options available before a consensus-wide migration is completed.
Bitcoin’s Quantum Debate Is Far From Over
The QSB experiment adds another proposal to an increasingly important discussion around Bitcoin’s long-term security.
Bitcoin has never needed to deal with a quantum computer capable of breaking its cryptographic assumptions. But preparing for that possibility involves more than simply designing a new signature scheme. Any network-wide transition would need to consider transaction sizes, wallet compatibility, user migration, consensus rules and the enormous amount of bitcoin already held across the blockchain.
QSB demonstrates one possible path without requiring an immediate protocol change. Its current limitations, including computational expense and its nonstandard nature, mean it is not yet a replacement for Bitcoin’s existing transaction system.
For now, the main takeaway is narrower but significant: a quantum-resistant Bitcoin transaction has been successfully mined on mainnet without modifying Bitcoin’s consensus rules.
That gives researchers and developers a real-world demonstration of what an opt-in quantum-defense mechanism could look like while the broader Bitcoin community continues to debate whether and how the network should eventually migrate to post-quantum cryptography.
