Headline: StarkWare researcher completes first “quantum-safe” Bitcoin transaction on mainnet — but it’s a limited, last-resort tool StarkWare on Aug. 26 confirmed that its researcher Avihu Levy successfully mined the first Bitcoin mainnet transaction using his Quantum-Safe Bitcoin (QSB) technique — a proof-of-concept showing you can construct Bitcoin transactions today that change the underlying attack assumptions for a specific output without altering consensus rules. What happened - Levy’s QSB spend was included in a mined block and accepted by Bitcoin’s existing consensus rules. That demonstrates QSB can be encoded in ordinary transactions without adding new opcodes, soft forks, or changes to nodes. - The transaction could not be propagated through the public mempool because QSB outputs exceed standard relay-policy limits; the first mainnet submission was routed directly to a miner via MARA’s Slipstream service. How QSB works (high level) - Standard Bitcoin transactions rely on elliptic-curve signatures (ECDSA or Schnorr). A large, fault-tolerant quantum computer running Shor’s algorithm could, in theory, derive private keys from exposed public keys. - QSB sidesteps that risk for a particular output by replacing the elliptic-curve security assumption with hash-based commitments. Instead of a normal signature, QSB constructs a hash-to-signature puzzle that can be verified using Bitcoin’s existing ECDSA verification opcodes but whose security rests on the preimage resistance of the RIPEMD-160 hash. - StarkWare’s implementation estimates roughly 118 bits of second-preimage resistance against a quantum-powered attacker using Shor’s algorithm. Costs and computation - Creating a QSB spend requires a large search: you must find transaction parameters whose RIPEMD-160 preimage parses as a valid DER-encoded signature. The search is computationally intensive and must be done for each transaction. - Levy’s codebase estimates the cloud-GPU search cost at roughly $75–$150; the accompanying paper gives a slightly wider $75–$200 range to account for implementation uncertainty. That cost covers off-chain computation only — fees to include the transaction on-chain are extra. - The search can be parallelized across GPUs, but every QSB output requires its own expensive search, and QSB scripts are large. What QSB does — and doesn’t — protect - QSB provides a way to protect coin holdings from future quantum attacks, but only if you move coins into a QSB output before a quantum adversary can extract keys from previously revealed public keys. - QSB works with legacy pre-SegWit scripts but does not directly protect Taproot outputs or Lightning Network channels. Coins must first be sent into a QSB-compatible output by a conventional transaction. - Addresses whose public keys were already exposed by prior spending (or that become exposed in the source transaction) remain vulnerable unless they are moved into QSB outputs before a capable quantum attacker acts. That leaves dormant coins and already-spent-key addresses outside QSB’s protection. Community response and caveats - Bitcoin security specialist Daniel Batten warned that claims QSB makes Bitcoin “quantum-safe” are overstated, noting it does not solve the dormant-address problem or previously exposed public keys. - Levy himself frames QSB as a “last-resort measure” rather than a scalable alternative to normal Bitcoin transactions: its compute cost, large scripts and reliance on miner-direct submission make it impractical for routine payments. - StarkWare CEO Eli Ben-Sasson called the successful transaction “reassurance” that holdings can be protected if the community wants a fallback option prior to any network-level changes. Alternatives and next steps - QSB does not use StarkWare’s STARK proving system, though both approaches are hash-heavy. Separately, zk‑STARKs are being explored as another route away from elliptic-curve assumptions, albeit with much larger proofs than many zk‑SNARKs. - Developers are also considering BIP-360 (Pay‑to‑Merkle‑Root) as a protocol-level mitigation that would reduce long-term quantum exposure — but that would require a consensus change. - StarkWare and Levy call for independent code review, additional mainnet testing, and further work on more scalable post-quantum signature systems. The QSB transaction provides a working fallback, but it does not eliminate the case for a coordinated, network-level migration to post-quantum-safe constructs. Bottom line The QSB mainnet spend is an important technical milestone: it proves you can build quantum-resistant Bitcoin outputs today without changing consensus. But it’s a narrowly targeted, costly tool — useful as an emergency option to protect high-value holdings, not as a drop-in replacement for everyday transactions. No publicly known quantum computer today can break Bitcoin keys, and broader, protocol-level solutions remain under consideration. Read more AI-generated news on: undefined/news