StarkWare researcher Avihu Levy completed a quantum-resistant Bitcoin transaction on mainnet, costing $150-$200 and bypassing standard relay rules via MARA's Slipstream.
Bitcoin & Blockchain Technology News
A researcher at blockchain firm StarkWare submitted a Bitcoin (BTC) transaction built to resist quantum computing attacks to the live Bitcoin network on Aug. 26, where it was confirmed in block 964,199.
The transaction spent a 10,000-satoshi output secured under a method called Quantum Safe Bitcoin (QSB), developed by StarkWare researcher Avihu Levy. MARA Pool mined the block. Because QSB transactions do not meet Bitcoin Core's standard relay criteria, the transaction was submitted directly through MARA's Slipstream service rather than the public mempool.
From Theory to On-Chain Demonstration
QSB uses hash-based one-time signatures combined with computational searches that bind transaction authorization to a single, specific transaction. The design is intended to prevent forgery in a scenario where a quantum computer can break the elliptic-curve cryptography that secures Bitcoin addresses and signatures today. Levy published the proposal in April 2026, describing it as a last-resort measure rather than a replacement for broader protocol changes.
The mainnet confirmation showed that Bitcoin's existing consensus rules can accommodate at least one form of quantum-resistant spending without a protocol change, moving Levy's April proposal from a paper exercise to an on-chain result.
Related Article: Ethereum Foundation Drops Poseidon Hash Function in Post-Quantum Shift
High Cost Limits Practical Use
The transaction was not cheap. StarkWare spokesperson Nathan Jeffay put the cost at roughly $150 to $200 in GPU computation, and the process took several hours to complete. Levy's original paper had estimated costs between $75 and $150, placing the actual mainnet result at the higher end of that range and slightly above it.
The cost and nonstandard classification keep QSB from working as a general solution. Ordinary Bitcoin nodes will not relay these transactions, and using the method requires direct access to a miner willing to accept out-of-band submissions.
The research gained urgency after Google published a March 2026 estimate that a capable enough quantum computer could derive a Bitcoin private key within nine to 12 minutes of the public key being exposed, a window that overlaps with Bitcoin's confirmation time. StarkWare CEO Eli Ben-Sasson said a protocol-level soft fork should still happen and that QSB is meant to serve as a safety net in the interim. Bitcoin developers are separately examining BIP-360, a proposed soft fork that would introduce a new output type and remove Taproot's quantum-vulnerable key-path spend option. QSB operates only at the individual transaction level and does not alter the network's cryptographic standard.
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