Coinbase · The Block
Coinbase quantum report flags exchange cold wallets among millions of bitcoin exposed by address reuse
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Coinbase's quantum advisory board says roughly 7 million bitcoin sit in addresses exposed to a future quantum attack, and that much of that exposure is not lost Satoshi-era coins but active funds, including cold wallets operated by known exchanges.
Key facts
- Bitcoin developers have separately floated the phased sunset of legacy signatures under BIP-361, and Google said in March it was setting a 2029 timeline for its own post-quantum cryptography
- About 1.7 million bitcoin sit across roughly 20,000 legacy pay-to-public-key (P2PK) addresses, where the public key itself is the address and is fully visible onchain, leaving those coins directly
- Provable Address-Control Timestamps, or PACTs, originally proposed by Paradigm researcher Dan Robinson, would let holders commit today to a future quantum-safe transfer without publicly moving funds
- Coinbase's quantum advisory board says roughly 7 million bitcoin sit in addresses exposed to a future quantum attack, and that much of that exposure is not lost Satoshi-era coins but active funds
Summary
The board splits the exposure into two buckets. The second and larger bucket is the one tied to address reuse. The report presents the argument that owners who have lost their keys do not need protection because they have already lost practical control of their coins, so the genuine question is what to do about holders who still control their funds but fail to move them before any migration deadline. The report sets out two opposing positions on solutions.