Quantum computers and Bitcoin — what is at risk and what is not

What is at risk

Bitcoin and Mobick use two kinds of cryptography:

• Hashing (SHA-256) — links blocks, powers mining, makes addresses. Quantum computers could speed up hash searches only modestly, so this is considered relatively safe.
• Signatures (elliptic curves) — sign with a private key, verify with the public key. The basics track said there is no way back from public to private key. With a strong enough quantum computer and Shor’s algorithm, that way back could open. This is the core threat.

So the question becomes: is my public key visible on the ledger?

Which coins go first

Early block rewards (P2PK)outputs locked directly to a public key, like 2009–2010 rewardsAddress that has spent beforea 1… or bc1q… address that has sent funds at least onceReceive-only addressa 1… or bc1q… address that has only receivedTaproot address (bc1p…)the (tweaked) public key is in the address itself

Private keysk

→

Public keypk

→

Address (hash)h(pk)

Receive-only 1… and bc1q… addresses show only a hash of the public key, so the key stays hidden until you spend. Early Bitcoin block rewards locked directly to public keys, which is why the roughly 1.1 million coins attributed to Satoshi are counted among the first exposed. It is also one more reason behind the old advice not to reuse addresses.

What to do about Satoshi’s coins

If quantum computers become real, Bitcoin faces a hard question: let someone crack and take the dormant early coins, or freeze or remove them first?

In March and April 2026 Oh predicted the debate: proposals from Wall Street to hard-fork away Satoshi’s and other lost early coins in the name of quantum safety, opposed by those who say “cracking them with an expensive quantum computer is still legitimate acquisition” — and, without agreement, a chain split. That is one person’s forecast, but what to do with dormant coins is clearly one of Bitcoin’s big unsolved problems.

What you can do now

• Don’t reuse addresses; use a new receiving address each time.
• Keep large amounts at receive-only addresses.
• Quantum-resistant signatures are under discussion among Bitcoin developers; when new formats arrive, follow your official wallet’s guidance.

Summary

• The core quantum threat is computing private keys from public keys (signatures); hashing and mining are relatively safe.
• Coins with exposed public keys (early P2PK, spent-from addresses) go first; Satoshi’s are the prime example.
• What to do with dormant coins is Bitcoin’s open problem, and whale hunting tries to answer it by signature.