Overview
- Google’s paper outlines how a powerful quantum computer could recover a Bitcoin private key in under nine minutes, faster than average block time, though no such machine exists today.
- Roughly 6.5 million BTC are in addresses a quantum attacker could target, including about 1.7 million coins in early addresses that already revealed their public keys on-chain.
- Developers are testing BIP-360 to keep public keys off the blockchain and reviewing post-quantum signatures like SPHINCS+ that are far larger than today’s, which could raise fees and squeeze block space.
- Tadge Dryja’s commit/reveal soft fork aims to protect the mempool—the waiting area for unconfirmed transactions—by recording a hash first and revealing the spend later to block forged races.
- No proposal is active, and ideas to throttle spending from legacy exposed addresses, such as the ‘Hourglass V2’ limit of one bitcoin per block, face resistance for curbing how people can spend their coins.