Bitcoin processed its first known quantum-resistant transaction on mainnet, mined through MARA’s private Slipstream mempool. The method, called Quantum Safe Bitcoin, was built by StarkWare’s Avihu Levy and closes a vulnerability that exposes a wallet’s public key during the roughly ten minutes it takes to confirm a transaction. The workaround uses hash-based proof-of-work puzzles instead of standard signatures, requiring no consensus rule change but only working with private mempools. MARA Foundation head Isabel Foxen Duke called it a stopgap, not a long-term solution. The urgency follows a Google paper warning that a quantum computer could break keys behind Ethereum’s richest wallets in under nine days.
Bitcoin executed its first known quantum-resistant transaction on mainnet today, mined through MARA’s private Slipstream mempool. The method, called Quantum Safe Bitcoin, was built by StarkWare’s Avihu Levy and closes a real gap in how Bitcoin protects funds in transit without asking the network to change a single consensus rule.
Bitcoin held behind a hashed P2PKH address is already safe from quantum attacks. The problem appears when the Bitcoin is spent, as the wallet’s public key sits exposed in the mempool for roughly ten minutes — exactly the window a quantum computer could exploit.
Levy built Quantum Safe Bitcoin to close that window without touching consensus. 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.
Levy first published the approach in an April paper, putting its security at around 118 bits under Shor’s algorithm. The estimated extra cost is a few hundred dollars in GPU time, and it fits inside Bitcoin’s existing script limit so no soft fork is needed.
The workaround requires a non-standard transaction format that only private mempools like Slipstream accept. MARA Foundation head Isabel Foxen Duke framed the mining as a stopgap: “We don’t believe private mempools are an appropriate long-term solution for Bitcoin quantum resistance.” She added 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. He called the result “a research quirk and not the straightforward way for Bitcoin to become” quantum-ready.
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. Researchers at Project Eleven flagged the same mempool-stage vulnerability that Quantum Safe Bitcoin targets.
Bitcoin developers have their own fix in the works, including a proposal called BIP-361 that would freeze old, quantum-vulnerable addresses in stages. Blockstream has taken a different route, running post-quantum signatures on its Liquid sidechain since April.
