Bitcoin confirmed the first mainnet transaction using researcher Avihu Levy's Quantum-Safe Bitcoin method on Aug. 26, according to StarkWare.
QSB Replaces Elliptic-Curve Security With Hash-Based Protections
The mined transaction demonstrated that QSB can operate under Bitcoin's existing consensus rules without requiring new opcodes, a soft fork or changes by Bitcoin nodes. Standard Bitcoin transactions rely on signatures using elliptic-curve cryptography. A sufficiently powerful quantum computer running Shor's algorithm could theoretically calculate a private key from its exposed public key. QSB changes the security assumptions for a particular output by using hash-based commitments and a hash-to-signature puzzle rather than depending on the difficulty of solving an elliptic-curve discrete logarithm.
The method uses Bitcoin's existing ECDSA verification operations as a vehicle, but its security comes from the preimage resistance of RIPEMD-160. The published implementation estimates approximately 118-bit second-preimage resistance against an attacker using Shor's algorithm. This development follows the broader push for quantum-safe crypto infrastructure, including the quantum-safe staking upgrade proposed for Ethereum.
QSB Required Off-Chain Computation and Miner Access
Creating a QSB spend involves searching for transaction parameters whose resulting RIPEMD-160 hash can be interpreted as a valid DER-encoded signature. Finding a suitable result requires approximately 2^46 hashing attempts. Levy's repository estimates that the search costs between $75 and $150 using cloud GPUs. Each transaction requires its own search, although the work can be divided across several GPUs. QSB transactions also exceed Bitcoin's standard relay policy limits, meaning ordinary nodes will not normally propagate them through the public mempool.
MARA's Slipstream service provided a direct route to a miner for the first mainnet transaction. This technical limitation echoes the security concerns surrounding hardware wallet vulnerabilities that prompted long-term holders to move Bitcoin in 2026.
The Transaction Does Not Make Bitcoin Quantum-Safe
The confirmed transaction proves that Bitcoin's consensus rules accept the QSB construction. It does not establish that Bitcoin, all existing addresses or the wider wallet ecosystem have become resistant to quantum attacks. QSB works with legacy pre-SegWit scripts but does not directly protect Taproot outputs or Lightning Network channels. Coins must also enter a QSB output through a conventional transaction before receiving its hash-based protection.
Bitcoin specialist Daniel Batten previously described broader claims that QSB already makes Bitcoin quantum-safe as an overstatement, citing its failure to address dormant coins and previously exposed public keys. Levy describes QSB as a last-resort measure rather than a scalable replacement for ordinary Bitcoin transactions. StarkWare CEO Eli Ben-Sasson said the successful transaction offers reassurance that holdings can be protected before a possible soft fork.
