StarkWare says quantum-safe Bitcoin transaction was mined on mainnet

QSB transaction reaches Bitcoin mainnet

StarkWare says a Bitcoin transaction using its Quantum Safe Bitcoin, or QSB, design was mined on the live network without changes to Bitcoin’s consensus rules.

The transaction was confirmed in block 964,199 on Aug. 26. Its inclusion on Bitcoin’s blockchain, the network’s public transaction record, is confirmed. However, the blockchain record does not prove that the design can resist quantum attacks.

Transaction details recorded onchain

• The transaction combined inputs of 39,179 satoshis and 10,000 satoshis.
• It created one output worth 44,000 satoshis.
• It paid a fee of 5,179 satoshis and measured 1,403 bytes.
• Mempool.space labeled it “Non-Standard” and “Not seen in Mempool.”
• MARA Pool mined the transaction. StarkWare said MARA’s Slipstream service gave it a direct path to a miner.

How the QSB design is intended to work

Researcher Avihu Levy’s open-source implementation says QSB uses Bitcoin’s existing legacy scripting rules, so it does not require a soft fork.

The design uses a hash-based one-time signature and a “hash-to-signature” puzzle. Levy says its security depends on resistance to finding a matching input for a RIPEMD-160 hash rather than on the difficulty of breaking an elliptic curve.

The documented process involves an offchain search over transaction values. The design estimates the chance of finding the required result at about one in 2^46 attempts. Two additional searches select groups of dummy signatures, while the final transaction extracts the required HORS preimages.

ECDSA remains in Bitcoin Script’s verification path. The implementation describes it as a vehicle for the process and says hashing provides the security-critical work. These are claims about the design, not an independent cryptographic assessment.

What the blockchain record confirms

The available onchain record confirms that transaction 305a24ff…ab07 was included in a Bitcoin block. StarkWare and Levy identify it as an implementation of QSB and describe it as quantum-safe.

The parent transaction containing the 10,000-satoshi output was confirmed on July 16. It measured 10,125 bytes and paid a 30,000-satoshi fee.

Quantum-resistance claim remains unverified

The transaction record does not independently establish that QSB can resist quantum attacks. The supplied material also does not include an outside cryptographic audit of the method.

StarkWare says QSB does not make Bitcoin as a whole quantum-safe. It is intended to protect coins only after they are moved into a special output. It does not add the claimed protection to ordinary holdings secured with ECDSA or Schnorr signatures.

StarkWare also said the method would not protect an address if its public key had already been exposed before the protective transaction was sent.

Design is presented as a limited fallback

Levy’s paper describes QSB as a last-resort measure. It says the required offchain computing and onchain costs would not scale to Bitcoin’s expected number of users or transaction volume.

The paper also says creating these transactions is more complicated than standard Bitcoin use. The method does not cover other uses such as Lightning Network channels.

The confirmed result is therefore narrow: a transaction identified by StarkWare and Levy as using QSB was mined. Ordinary Bitcoin holdings and Bitcoin’s consensus rules were not changed.

Source

• The Defiant