On August 26, the StarkWare team, behind the L2 solution Starknet, successfully conducted a transaction on the Bitcoin mainnet that is resistant to attacks using quantum computers. Notably, this did not require changes to the consensus rules of the first cryptocurrency.
The essence of the QSB experiment
The experiment was implemented as part of the Quantum Safe Bitcoin (QSB) initiative, developed by Avihu Levi, Head of Product at StarkWare. The concept, presented back in April, was conceived as an emergency mechanism for migrating coins before the implementation of full post-quantum protection at the protocol level. Engineer Tomer Giladi helped bring the idea to life, with Binohash from BitVM creator Robin Linus used as the technical foundation.
The QSB mechanism adds an additional layer to Bitcoin's standard protection based on hash functions, which remain resistant to quantum threats. The signature grinding technique involves enumerating many transaction variants until the desired cryptographic properties are achieved. The bulk of the computation is performed off-chain, with the security of the result relying on the difficulty of inverting the hash.
It is worth emphasizing that the method remains expensive and slow: preparing a single operation can take several hours and cost hundreds of dollars in computational resources. Due to the non-standard transaction format, it was not relayed through the public mempool, so it was sent directly to a miner via the MARA Slipstream service.
Limitations and prospects
StarkWare notes that the experiment does not make the entire Bitcoin network quantum-resistant. QSB allows individual coins to be moved to an output with additional protection without affecting the protocol itself. The method is also useless for coins whose public key was previously exposed — in this case, an attacker would have had enough time to analyze it before the protected transaction was sent.
StarkWare CEO Eli Ben-Sasson still considers a soft fork the preferred long-term solution. "Avihu took this on in his spare time, out of personal interest, and has now shown that Bitcoin has no expiration date. The successful transaction gives Bitcoin confirmation that funds can be protected even before that moment," he stated.
Recall that in late July, Cardano founder Charles Hoskinson suggested that Bitcoin could lose its leadership due to the quantum threat. StarkWare is already implementing post-quantum protection in Starknet, presenting a three-stage plan to replace dependencies on elliptic curves.
My comment: This experiment is an important step, demonstrating the practical viability of quantum-resistant solutions in Bitcoin without a hard fork. However, the high cost and complexity of the method limit its application, and it is unlikely to become a mass-market tool. Real network protection will still require a consensus update, and the sooner the community begins discussing it, the safer Bitcoin's future will be.