StarkWare Confirms Quantum‑Safe Bitcoin Transaction on Mainnet

StarkWare announced that a Bitcoin transaction built with its Quantum Safe Bitcoin (QSB) design was mined on mainnet without altering Bitcoin’s consensus rules. The transaction (hash 305a24ff…ab07) was included in block 964,199 on August 26.

On‑chain Details

Blockstream’s data shows the transaction combined a 39,179‑satoshi input with a 10,000‑satoshi input, created a single 44,000‑satoshi output, and paid a 5,179‑satoshi fee. The transaction size was 1,403 bytes.

How QSB Works

According to the open‑source implementation by researcher Avihu Levy, QSB relies on Bitcoin’s existing legacy scripting rules and does not require a soft fork. The design uses a hash‑based one‑time signature and a “hash‑to‑signature” puzzle that depends on RIPEMD‑160 preimage resistance rather than elliptic‑curve hardness.

• Off‑chain search over sequence and locktime values until the RIPEMD‑160 hash of a transaction‑bound public key resembles a valid DER‑encoded ECDSA signature (estimated probability ≈ 1 in 2^46).
• Two additional search rounds select dummy signatures; the chosen indices form a compact identifier for the transaction.
• The final assembly extracts HORS preimages, while ECD5A remains only a verification vehicle in Bitcoin Script.

Limitations and Scope

The method protects coins only after they are moved into the special QSB output; it does not retrofit quantum resistance onto existing ECDSA‑ or Schnorr‑secured holdings, nor does it help addresses whose public keys were already exposed.

The transaction was classified as non‑standard, required a direct mining path, and was mined by MARA Pool using its Slipstream service.

Verification Status

The blockchain record confirms that the transaction was mined. The quantum‑resistance claim rests on StarkWare’s and Levy’s statements; the on‑chain data does not independently verify the cryptographic security properties.