The Bitcoin Beacon
An estimated 6.9 million bitcoin sit in addresses that have already shown their public keys. BitGo is now scoring them.
No quantum computer can steal a bitcoin today. BitGo's argument, published on July 9 alongside a set of new custody tools, is that this is the reason to act rather than the reason to wait.
The custodian — now NYSE-listed under BTGO — shipped four features for UTXO-based wallets on its multi-signature service: a Quantum Risk Score that rates exposure across supported bitcoin wallets, a workflow that walks clients off compromised addresses, a UTXO selection method that groups coins by address to limit what a partial spend reveals, and changed default address-type controls.
A bitcoin address is a hash of a public key. Until you spend from it, the public key stays hidden and a future quantum machine has nothing to attack. Spend once, and the public key is published forever in the transaction that moved the coins. Reuse that address, and whatever is left sits behind a key an adversary can already see.
Estimates put roughly 6.9 million BTC in addresses with exposed public keys. Some are lost coins from the network's first years, when pay-to-public-key was standard. Some are the change outputs of people who did not know address reuse mattered.
“We believe the safest key is one whose public key has never been revealed on-chain.” — Mike Belshe, BitGo
The scope is narrower than the headline. Address types that reveal a public key from the moment of creation — pay-to-public-key, and Taproot — fall outside the application and need separate remediation. Taproot matters here: it is the address type the network has been migrating toward, and it publishes the key at funding.
BitGo describes the release as a complement to eventual protocol-level post-quantum signatures, not a substitute. That is honest. Custodial hygiene protects a custodian's clients. It does nothing for the 6.9 million coins nobody custodies, most of which will never move because nobody holds the keys.
Protocol change is slow by design, as the BIP-110 filter fight has spent this summer demonstrating. BIP-360 and BIP-361, the post-quantum address proposals, have no activation path and no consensus, and the June White House executive order on post-quantum cryptography created a compliance deadline for institutions long before it created one for bitcoin.
Custodians have a simpler decision loop: they can change defaults on Thursday. Adam Back, whose BSTR treasury company collapsed the same week, framed the timing in the announcement: “Nobody has a quantum computer that can touch Bitcoin today, but that's exactly why the work should start now, while it's calm and optional rather than urgent and forced.”
Skeptics will note that a firm selling custody services has an interest in a risk only custody services can manage. Both things can be true.
Quantum risk in bitcoin is a key-hygiene problem before it is a cryptography problem. The first firms to treat it that way are the ones with clients to lose.
Editor’s note: the 6.9 million BTC figure is an estimate cited by BitGo via Talos and varies by methodology across published analyses. Adam Back is quoted from the company’s own announcement.
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