Bitcoin Lands First Quantum-Resistant Transaction via StarkWare's QSB Method

StarkWare engineer Avihu Levy successfully executed Bitcoin's first quantum-safe transaction on its mainnet, confirmed on August 26. The method, called Quantum-Safe Bitcoin (QSB), adds a hash-based lock to Bitcoin without requiring any soft fork or consensus change.

The current signatures used by Bitcoin depend on elliptic curve cryptography, which can be broken using a powerful quantum computer. This leaves public keys vulnerable to being recovered and stolen. Levy's QSB method uses signature grinding, a technique that produces a valid Bitcoin signature without requiring a private key. This costs between $75 to $150 per transaction.

StarkWare CEO Eli Ben-Sasson framed the achievement as proof that quantum protection does not require waiting on a network upgrade. He noted that while QSB transactions are nonstandard and cannot travel through the ordinary mempool, they can be sent directly to cooperating miners. The method only protects addresses whose public key has not already been published before broadcast.

StarkWare's own technology, built on ZK-STARKs, already rests on hash-based assumptions rather than elliptic curves. Starknet's native account abstraction lets accounts switch signature schemes without a network-wide protocol change, and post-quantum accounts are already active on Starknet mainnet.