StarkWare Completes Bitcoin’s First Quantum-Safe Transaction

Highlights:

• StarkWare says Bitcoin’s first quantum-safe mainnet transaction shows holders can protect funds without changing Bitcoin’s protocol.
• The QSB method uses hash-based protection and signature grinding to reduce risks from future quantum attacks.
• StarkWare says the method offers an early defense while developers work on broader long-term Bitcoin protection.

Bitcoin (BTC) has recorded what StarkWare says is the first quantum-safe transaction on its main network. The new method aims to protect Bitcoin from a future attack by powerful quantum computers, without changing Bitcoin’s current consensus rules. The transaction did not use a quantum computer. Instead, StarkWare used today’s computing technology to create a Bitcoin transaction designed to resist future quantum attacks.

StarkWare announced the development on August 26. Researcher Avihu Levy, General Manager of Applications at StarkWare, designed the Quantum-Safe Bitcoin, or QSB, method. He first published the research in April. StarkWare engineer Tomer Giladi later helped turn the idea into a working Bitcoin mainnet transaction.

🚨 FIRST QUANTUM-SAFE $BTC TRANSACTION ON MAINNET.

A StarkWare researcher has reportedly executed a Bitcoin transaction designed to resist future quantum-computing attacks.

No Bitcoin consensus changes required.

Still experimental, but this could be an important early step in… pic.twitter.com/YmbJuDTOoQ

— Wise Advice (@wiseadvicesumit) August 27, 2026

Quantum-Safe Bitcoin Method Works Without a Protocol Change

Bitcoin currently uses elliptic curve cryptography to protect transactions. This system is considered secure with today’s computers. However, a powerful enough quantum computer could one day use Shor’s algorithm to break this protection and recover a private key from a public key.

The risk becomes more serious when someone spends Bitcoin. A Bitcoin address can hide the public key until the owner makes a transaction. Once the transaction is sent, the public key becomes visible while miners prepare to confirm it. A future quantum attacker could potentially use that short period to calculate the private key and try to move the same Bitcoin first. QSB aims to close that gap. It adds another layer of protection based on hash functions rather than the elliptic curve system that Bitcoin normally uses.

The method works with Bitcoin as it exists today. It does not require a hard fork or soft fork before users can use the approach. However, StarkWare still believes a soft fork would provide a better long-term solution for protecting Bitcoin from quantum threats.

QSB Uses Bitcoin’s Existing Tools

The method uses a process called signature grinding. Before broadcasting the transaction, the sender performs computational work to find a transaction hash that Bitcoin can accept as a valid signature. The work happens off-chain before the transaction reaches Bitcoin. According to StarkWare, running the process currently costs several hundred dollars.

QSB transactions also use a nonstandard format. As a result, they cannot currently travel through Bitcoin’s normal mempool like regular transactions. The first transaction instead reached a miner through MARA Slipstream, which provides a direct route for certain transactions. 

However, QSB does not make the entire Bitcoin network quantum-safe. It protects Bitcoin moved into a specific type of output that relies on hash-based security. It also cannot protect coins if their public key was already exposed before the QSB transaction was created.

StarkWare Still Supports a Longer-Term Bitcoin Upgrade

StarkWare CEO Eli Ben-Sasson said the successful transaction gives Bitcoin holders another option while developers work toward broader protection.

He said:

“What today’s successful transaction offers Bitcoin is a reassurance that holdings can be protected before that happens.”

StarkWare also made the research paper and QSB implementation open source. The company said the mainnet transaction shows that Bitcoin holders may have a way to prepare for future quantum computing risks without waiting for an immediate change to Bitcoin’s protocol.

Google Quantum AI researchers also warned about the future quantum risk to Bitcoin. Their study, published in PRX Quantum on August 21, found that Shor’s algorithm could break the secp256k1 elliptic-curve protection used by Bitcoin with about 1,200 to 1,450 logical qubits, depending on the computational approach. Such quantum computers do not exist today.