Bitcoin got its first known quantum-resistant transaction on mainnet today, mined through MARA’s private Slipstream mempool using a method called Quantum Safe Bitcoin, built by StarkWare’s Avihu Levy.

It closes a real gap in how Bitcoin protects funds in transit, without asking the network to change a single consensus rule, though even the people behind it call it a stopgap rather than a fix.

How Quantum-Safe Bitcoin Closes the Mempool Gap

Bitcoin held behind a hashed address, the P2PKH format most wallets use, is already considered safe from quantum attacks. The problem shows up the moment someone spends it.

Sending Bitcoin means revealing the wallet’s public key, and that key sits exposed in the mempool for roughly the ten minutes it takes to confirm, exactly the window a quantum computer could exploit.

Levy built Quantum Safe Bitcoin to close that window without touching consensus rules. The scheme modifies Binohash, a technique from BitVM creator Robin Linus, wrapping each transaction in a proof-of-work puzzle whose security rests on hash functions believed to resist quantum attacks rather than on the signature itself.

Levy first published the approach in an April paper, putting its security at around 118 bits under Shor’s algorithm, roughly half that under Grover’s, with an estimated extra cost of a few hundred dollars in GPU time.

It fits inside Bitcoin’s existing script limit, so no soft fork is needed, though it does require a non-standard transaction format that only private mempools like Slipstream will accept. MARA Foundation head Isabel Foxen Duke framed the mining of the transaction as a stopgap rather than an endorsement of private mempools long-term.

“We don’t believe private mempools are an appropriate long-term solution for Bitcoin quantum resistance,” she said, adding that MARA is willing to keep supporting Slipstream for break-glass cases while the network works toward a consensus-level change.

Levy credited StarkWare’s Tom Giladi with finishing the execution, building on earlier work from Linus and Ethan Heilman, but was careful to call the result “a research quirk and not the straightforward way for Bitcoin to become” quantum-ready.

Why the Rest of the Industry Is Racing on This

The urgency traces back to a Google paper from earlier this year, which found that a sufficiently powerful quantum computer could break the private keys behind Ethereum’s 1,000 richest wallets in under nine days, as CryptoPotato reported in March.

Researchers at Project Eleven flagged the same mempool-stage vulnerability Quantum Safe Bitcoin is targeting, warning that funds could be intercepted from a transaction before it even clears. But Bitcoin developers have their own fix in the works too, including a proposal called BIP-361 that would freeze old, quantum-vulnerable addresses in stages, starting with new deposits and eventually blocking withdrawals.

Blockstream has taken a different route, running post-quantum signatures on its Liquid sidechain since April so users can opt into protection without waiting on Bitcoin’s own upgrade path.

Source: CryptoPotato