StarkWare executes first quantum-safe Bitcoin transaction on mainnet

StarkWare has successfully carried out the first quantum-safe Bitcoin transaction on the Bitcoin mainnet. The method, developed by researcher Avihu Levy, protects transactions against attacks from quantum computers and requires no changes whatsoever to the Bitcoin protocol or its consensus rules. This is remarkable, because it was long assumed that quantum security for Bitcoin would only be possible through a protocol change.

Bitcoin is available at OKX and Bybit.

In short:

• The first quantum-safe Bitcoin transaction has been carried out on the mainnet without any protocol change.
• The method, called Quantum-Safe Bitcoin (QSB), replaces elliptic curve cryptography with security based on hash functions.
• The approach is experimental and costs around $75 to $150 per transaction in computing power off the blockchain.

What QSB does and why it matters

Bitcoin currently uses elliptic curve cryptography to secure transactions. The problem is that Shor’s algorithm, running on a sufficiently powerful quantum computer, can quickly solve this type of mathematical problem. This would, in theory, allow an attacker to derive a private key from a public key as soon as the latter becomes visible.

That moment of vulnerability occurs when a transaction sits in the mempool: the signature then reveals the public key, and a quantum computer could, in that brief window, work out the private key and spend the coins first. QSB closes this window by adding, alongside the existing security, a second quantum-resistant lock based on hash functions. Shor’s algorithm cannot break hash functions.

Technically, QSB uses a technique called signature grinding, in which a valid Bitcoin signature is created without a private key. The security thus rests on the difficulty of reversing a hash function rather than on the secrecy of a private key. This computation takes place off the blockchain, before the transaction is sent, and currently costs several hundred dollars in GPU computing power.

Limitations and the road to a soft fork

QSB does not make Bitcoin as a whole quantum-safe. What has been demonstrated today is that a specific construction works on the mainnet, while the network itself remains unchanged. The method also does not help for addresses whose public key has already been published, because an attacker would already have had time to derive the private key.

In addition, QSB transactions use a non-standard format, meaning they are not propagated through the regular mempool. For this first transaction, use was made of MARA Slipstream as a direct route to a miner. Avihu Levy designed the method in his spare time and published the research in April 2026. StarkWare engineer Tomer Giladi then developed it into a working transaction.

According to StarkWare, a soft fork remains the better solution in the long term. CEO Eli Ben-Sasson says that Levy has shown with this project that Bitcoin has no expiry date, but that he still expects the Bitcoin community to ultimately opt for a soft fork. What the successful transaction now offers is the certainty that holdings can be protected even before such a soft fork exists.