StarkWare says Bitcoin has reached a major milestone in its race against quantum computing. The company confirmed that a quantum-safe transaction was mined on the Bitcoin mainnet on August 26, marking the first live demonstration of its Quantum Safe Bitcoin construction.
The transaction shows that Bitcoin can support a quantum-resistant spending method without changing its consensus rules. However, the development does not make the Bitcoin network fully quantum-safe.
Quantum Risk Meets a Live Bitcoin Transaction
Bitcoin currently relies on elliptic-curve cryptography for transaction signatures. A sufficiently powerful quantum computer running Shor’s algorithm could eventually derive private keys from exposed public keys. That could put some Bitcoin holdings at risk.
StarkWare researcher Avihu Levy developed Quantum Safe Bitcoin, or QSB, to address this vulnerability using Bitcoin’s existing scripting capabilities. The method adds a hash-based security layer that does not depend on elliptic-curve assumptions.
QSB uses a technique called signature grinding. Instead of producing a conventional private-key signature, the sender performs substantial computation to find a transaction hash that satisfies the required conditions. The resulting security depends on hash preimage resistance rather than the secrecy of an elliptic-curve private key.
A Costly Lifeboat, Not a Permanent Fix
The break through comes with significant limitations. Producing a QSB transaction requires expensive off-chain computation, with the original research estimating costs of several hundred dollars under its assumptions.
The transaction also uses a nonstandard format. Ordinary Bitcoin nodes do not relay it through the normal mempool process, so StarkWare relied on MARA’s Slipstream service to deliver the transaction directly to a miner.
StarkWare continues to favor a Bitcoin protocol upgrade as the long-term solution. The company has also participated in BIP 360, a proposal aimed at enabling quantum-resistant Bitcoin script functionality through a soft fork.
The mainnet demonstration therefore represents a practical emergency option rather than a complete network upgrade. Still, it moves quantum-resistant Bitcoin protection from research into real-world execution and gives holders another potential path before quantum computers become capable of threatening existing cryptographic protections.
