Bitcoin Executes First Quantum‑Safe Mainnet Transaction

Bitcoin’s network recorded its first quantum‑safe transaction on August 26, using a method developed by researcher Avihu Levy. The transaction was confirmed without any changes to Bitcoin’s consensus rules, soft forks, or new opcodes.

How the Quantum‑Safe Bitcoin (QSB) Method Works

QSB replaces the elliptic‑curve security assumptions of standard Bitcoin signatures with hash‑based commitments. It creates a transaction whose RIPEMD‑160 hash can be interpreted as a valid DER‑encoded signature, relying on the pre‑image resistance of the hash function rather than the difficulty of solving an elliptic‑curve discrete logarithm.

Off‑Chain Computation and Miner Submission

Generating a QSB spend requires extensive off‑chain computation, estimated at $75–$150 (or up to $200) using cloud GPUs. The search involves roughly 2.46 × 10^46 hashing attempts. Because QSB transactions exceed standard relay limits, they are not propagated through the public mempool and must be submitted directly to a participating miner, as was done via MARA’s Slipstream service for the first mainnet transaction.

Scope and Limitations

• QSB protects legacy pre‑SegWit outputs but does not secure Taproot outputs, Lightning Network channels, or coins that have already exposed public keys.
• Coins must first be moved into a QSB‑compatible output via a conventional transaction before gaining hash‑based protection.
• The method is considered a “last‑resort” measure due to its computational cost, large scripts, and reliance on direct miner submission.

Implications for Bitcoin’s Quantum Resilience

The successful transaction shows that Bitcoin’s existing consensus can accept QSB constructions, offering a fallback protection mechanism. However, it does not make the entire network quantum‑safe, and a broader protocol‑level upgrade remains under study. Developers are also exploring alternatives such as BIP‑360, which would require a soft fork.