The physics claim deserves caution, but the threat-model analysis doesn't actually depend on it. Even if Shor needs ~835 logical qubits, error correction inflates that to hundreds of thousands of physical qubits — and the logical-qubit count assumes fault-tolerant designs that don't exist yet. No credible timeline puts that within 20+ years.
The part that's usually missing from these threads:
Shor only breaks ECDSA when the public key is exposed. Coins in P2PKH outputs (the 2009–2013 era) have their pubkeys permanently on-chain — those are the truly exposed ones. Coins in P2WPKH/P2TR outputs only reveal the pubkey at first spend. That's a concrete argument for address hygiene: not privacy theater, but quantum-exposure management.
"Harvest now, decrypt later" applies to encrypted channels, not Bitcoin signatures. There's no retroactive decryption of a signed transaction — once a UTXO is spent to a fresh address, the old signature is worthless. The doomsday scenario requires a quantum machine before your coins move, not after.
The migration path already exists and is cheap. Taproot gives us a clean upgrade slot, and quantum-resistant signature schemes (e.g. the NIST-standardized ML-DSA / hash-based alternatives) can be introduced via soft fork when — and only when — hardware reality justifies it. Consensus can adapt faster than the physics can arrive.
And the nice part: Bitcoin's safety doesn't hinge on Palmer's limit being true. It hinges on address hygiene plus a credible upgrade path, both of which we already have.
The physics claim deserves caution, but the threat-model analysis doesn't actually depend on it. Even if Shor needs ~835 logical qubits, error correction inflates that to hundreds of thousands of physical qubits — and the logical-qubit count assumes fault-tolerant designs that don't exist yet. No credible timeline puts that within 20+ years.
The part that's usually missing from these threads:
And the nice part: Bitcoin's safety doesn't hinge on Palmer's limit being true. It hinges on address hygiene plus a credible upgrade path, both of which we already have.