StarkWare secures Bitcoin with quantum-safe method on mainnet

A StarkWare researcher just pulled off something the Bitcoin community has debated for years: locking coins in a vault that no quantum computer, present or future, can crack. And he did it on Bitcoin’s live network, using existing rules, without asking anyone’s permission.

The first quantum-safe Bitcoin transaction was confirmed in block 964,199 on August 26, 2026. It spent a modest 10,000 satoshis, cost 5,179 satoshis in fees, and weighed in at 1,403 bytes.

How it works without changing Bitcoin

The transaction was executed by Avihu Levy, StarkWare’s General Manager of Applications, who published an open-source implementation of the method back in April 2026. The core idea is deceptively simple: replace the elliptic-curve cryptography that Bitcoin normally uses for signatures with hash-based constructions instead.

Bitcoin’s current security relies on elliptic-curve discrete-log hardness. Quantum computers could eventually solve it using Shor’s algorithm, potentially exposing funds secured by publicly revealed keys.

The quantum-safe Bitcoin (QSB) approach swaps that foundation for hash preimage resistance, which remains robust even against quantum attackers. The result is approximately 118-bit second-preimage resistance under a quantum threat model.

The transaction operates within Bitcoin’s existing script and opcode structures. Levy used the MARA Slipstream method to get the non-standard transaction mined, essentially bypassing ordinary node relay rules while still playing by consensus rules.

StarkWare CEO Eli Ben-Sasson said the achievement allows Bitcoin holders to secure their coins in a quantum-resistant manner, providing immediate safeguards while a longer-term soft-fork solution is developed.

The cost of quantum safety

Each quantum-safe transaction requires off-chain GPU computation estimated to cost between $75 and $150. That’s not pocket change for someone moving 10,000 satoshis, but it starts looking very reasonable if you’re securing millions of dollars in Bitcoin.

The parent funding transaction of 10,000 satoshis was confirmed back on July 16, 2026, more than five weeks before the quantum-safe spend was mined.

One critical limitation: the QSB method only protects funds that have been deliberately transferred into the designated quantum-safe output format. Your existing Bitcoin sitting in a standard address with an exposed public key remains vulnerable. The approach is opt-in protection, not a blanket fix.

An estimated 7 million BTC currently face exposure risk due to publicly visible keys in the existing UTXO set.

StarkWare’s broader quantum play

Levy’s research paper detailing quantum-safe transactions without soft forks was published on April 9, 2026. By June 2026, StarkWare had unveiled a three-phase post-quantum roadmap for Starknet, its Layer 2 scaling network.

Ben-Sasson explicitly framed QSB as a bridge to a soft fork, not a replacement for one. The $75-to-$150 compute cost per transaction, the non-standard mining requirement, and the opt-in nature of the protection all point to practical limitations that a consensus-level change could eventually eliminate.

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