The Debate Over Quantum-Resistant Signatures in Bitcoin

Many are assumed to belong to Bitcoin’s pseudonymous creator Satoshi Nakamoto and other owners who lost their keys, which means they can never be moved to safety. Another 5 million or so are exposed through address reuse, according to Project11, a research group tracking the issue, though most of those are thought to be active holdings in exchange wallets.

Swapping in quantum-resistant signatures is the easy part, but the fight is over the coins nobody moves. One camp argues for a hard deadline, after which the signature schemes Bitcoin uses today, ECDSA and Schnorr, stop being accepted and any unmigrated coins become unspendable. Leaving them live, this side says, hands a future attacker, potentially a sanctioned state like North Korea, a stash of bitcoin large enough to crash the price and taint the network’s legitimacy.

The other camp calls that confiscation, a violation of the absolute property rights Bitcoin was built on, and warns it sets a precedent for freezing coins under government pressure later.

Between them sit the several proposals CoinDesk has tracked over the past two months.

Hourglass would cap how many vulnerable coins can be spent per block to prevent a supply flood. BIP-361, from developer Jameson Lopp and others, would let migrated holders prove ownership after the cutoff with a quantum-resistant proof that exposes no key. PACTs, from Paradigm’s Dan Robinson, would let owners timestamp a private claim now and move funds later without revealing anything today.