StarkWare Demonstrates First Quantum‑Safe Bitcoin Transaction on Mainnet

StarkWare announced that a Bitcoin transaction employing a quantum‑safe construction was successfully mined on the live network, representing the first such instance on mainnet.

Transaction Details

The on‑chain data shows the transaction spent a 10,000‑satoshi output (approximately $8 at current prices) and paid a fee of 5,179 satoshis. The transaction was included in block 964,199 by the MARA Pool.

How the Quantum‑Safe Method Works

The method, called Quantum‑Safe Bitcoin (QSB), adds a hash‑based lock next to the standard elliptic‑curve signature that protects a Bitcoin output. Because Shor’s algorithm cannot break hash functions, the security of the spend relies on the difficulty of reversing a hash rather than on keeping a private key secret.

Researchers generate a valid signature without a private key by "grinding" off‑chain: they repeatedly hash candidate transactions until the resulting hash itself forms a correctly formatted signature. This approach builds on the Binohash technique developed by Robin Linus.

Limitations of the Current Approach

• Prior exposure: Addresses whose public keys are already on‑chain do not benefit, as a quantum adversary could derive the private key from the published public key.
• Migration step: To create a hash‑secured output, the coins must first be sent in a normal transaction, which reveals the sending address’s public key. The output spent in the demonstrated transaction was funded by such a prior transaction in July.
• Delivery constraints: QSB transactions use a nonstandard format, meaning regular nodes will not relay them. The MARA Slipstream service provided the necessary routing to a miner.

Cost Considerations

The off‑chain computation required for the grinding process is estimated at $75‑$150, while StarkWare reported that the overall transaction cost reached several hundred dollars.

Outlook

StarkWare’s blog notes that while this demonstration shows a possible path to quantum‑resistant Bitcoin holdings without a protocol change, a soft‑fork upgrade remains the preferred long‑term solution. Bitcoin has not yet adopted any protocol‑level quantum‑safety measures.