A StarkWare researcher has mined what the company describes as the first quantum-safe transaction on the Bitcoin mainnet, showing that holders could move coins into storage a working quantum computer cannot open without waiting for a soft fork. The milestone, detailed in StarkWare’s announcement, required no change to Bitcoin’s consensus rules.
A second lock built on hash functions
The construction, called Quantum-Safe Bitcoin (QSB), was designed by Avihu Levy, a researcher and General Manager of Applications at StarkWare who published the underlying research in April 2026 and built it on his own time. Bitcoin’s ordinary signatures rest on elliptic-curve cryptography, the class of math that Shor’s algorithm could solve on a large enough quantum computer. QSB adds a second quantum-resistant lock built on hash functions instead, using a technique known as signature grinding to produce a valid Bitcoin signature without a private key.
Because the transaction uses a non-standard format, it does not travel through the ordinary mempool and needed a direct path to a miner, which MARA Slipstream provided. StarkWare says the approach currently costs several hundred dollars in off-chain computation and draws on Binohash, a technique developed by BitVM creator Robin Linus.
Why the timing matters for Bitcoin
The demonstration arrives as the industry races to address quantum risk. Bitcoin’s elliptic-curve signatures have long been its best-known theoretical vulnerability, and earlier research has shown how coins whose public keys are exposed could be recovered once a capable machine exists. Running the QSB construction on mainnet is a signal that quantum-resistant options are moving from paper to practice rather than waiting on a protocol upgrade.
What remains experimental
QSB does not make Bitcoin itself quantum-safe, and StarkWare is explicit about the limits. The network is unchanged; the technique protects only coins moved into a hash-based output, and it would not help an address whose public key was already published before the transaction was sent. StarkWare CEO Eli Ben-Sasson said the result shows “Bitcoin has no expiration date,” but added: “I still want Bitcoin to choose to do a soft fork and I expect we will get one.” The company frames QSB as a stopgap reassurance, alongside its separate push to scale Bitcoin, rather than a substitute for consensus-level fixes.
