BTC security under “harvest now, decrypt later” quantum threat

Security investor Andrew Gault (ZeroTier) says BTC security risks extend beyond wallet hacks to the encrypted identity, authentication, and digital-signature layers used by exchanges, bridges, and custodians. The core issue is “harvest now, decrypt later”: attackers can collect encrypted inter-system traffic, authentication records, and proofs today, then decrypt or forge them once quantum capabilities improve. A Google study cited in the report claims a sufficiently powerful quantum computer could extract BTC private keys from public addresses in as little as nine minutes, renewing focus on the ~6.9M BTC reportedly held on public addresses and the lack of an industry-wide post-quantum migration plan. Google reportedly targets post-quantum cryptography completion by 2029, prioritizing wire-level signing and authentication. But major exchanges and custody providers have not publicly committed to similar timelines for updating their signing infrastructure. Ethereum (ETH) is mentioned as starting community-driven post-quantum efforts. Risk modelling: Citi estimates a quantum-enabled attack against a top U.S. bank could trigger $2T–$3.3T in financial-system cascade losses, while the Global Risk Institute puts the probability of cryptographically relevant quantum computing by 2034 at 19%–34%. CoinShares analysis is used to temper panic, arguing that fears of direct BTC wallet key breaches may be overstated and that any immediate market impact could be limited (fewer than ~10,000 BTC), but the report still flags “proof-layer” weaknesses as a likely BTC security exposure path. For traders, this keeps BTC security in the spotlight: the headline is bearish sentiment risk, yet near-term price impact may remain limited unless exchanges/custodians provide concrete post-quantum timelines.