Bitcoin Completes First Quantum Resistant Transaction

StarkWare says it has completed the first quantum resistant $BTC transaction on Bitcoin's mainnet, marking a practical step forward in the effort to harden the network against quantum computing threats.

How the Transaction Works

The method relies on a technique called signature grinding. While a transaction waits in Bitcoin's mempool, the approach repeatedly generates signatures until finding one specifically designed to reduce the window of exposure to a potential quantum attack. The scheme works entirely within Bitcoin's existing consensus rules, requiring no softfork, no protocol upgrade, and no community coordination.

Standard Bitcoin transactions use a digital signature scheme called ECDSA to prove ownership of funds. A quantum computer running Shor's algorithm could reverse-engineer that signature process, deriving private keys from public keys and stealing coins. The signature grinding approach aims to limit that vulnerability without touching the protocol itself.

Because the method shifts security from signatures to computation, every transaction requires heavy off-chain GPU processing, with costs estimated at $75 to $200 per transaction. StarkWare frames it as an emergency-ready tool rather than a permanent fix for the broader network.

Why MARA's Slipstream Was Needed

Because the transaction uses an unusual format, it cannot travel through standard node relay. StarkWare said MARA mined the transaction using its Slipstream service. Slipstream is a direct transaction submission service on Bitcoin, powered by Marathon and made possible by the company's proprietary mining pool, MARA Pool. It is designed to streamline confirmations of large or non-standard Bitcoin transactions.

By default, Bitcoin nodes frequently exclude large and non-standard transactions from Bitcoin's mempool, even if these transactions adhere to the Bitcoin network's consensus rules. As a result, complex Bitcoin transactions are often delayed or unprocessed. Slipstream bypasses that limitation by allowing direct submission to MARA's pool.

Widespread adoption of the quantum resistant approach would still require changes to how standard nodes handle these transaction types. Most paths to hardening Bitcoin against quantum attacks, including BIP-360 and hash-based signature schemes like SPHINCS+, require protocol-level changes that must navigate Bitcoin's notoriously slow and contentious governance process. StarkWare's method sidesteps that for now, but broader rollout would need the network to follow.

Avihu Levy, chief product officer at StarkWare and co-author of BIP-360, released a full research paper and open-source implementation on April 9, 2026. Levy also co-authored BIP-360, the quantum-resistant address proposal that was merged into Bitcoin's official BIP repository in February, a proposal that, unlike the signature grinding approach, would require a softfork.

Sources:
CoinDesk: Quantum-Safe Bitcoin Now Possible Without a Soft Fork
MARA Investor Relations: Marathon Digital Holdings Launches Slipstream
The Defiant: StarkWare Researcher Publishes Quantum-Safe Bitcoin Transaction Scheme