# CatBitcoin

> Until you spend — or you used Taproot — the public key is in the box. No prices. No panic. England of the metaphor: this is a hash, not superposition.

The checker at https://catbitcoin.com/schrodingers-wallet-checker/ classifies a mainnet address as closed or open. It looks up public spend history on blockstream.info. Never paste a seed phrase.

## The box

- Closed: a 1, 3, or bc1q address that has never spent. Only a hash of the public key is on-chain.
- Open: a prior spend published the key; or Taproot (bc1p), which publishes the key on receipt; or older P2PK outputs, open since creation.
- Open is not an emergency. No existing quantum computer can break secp256k1 in time to steal coins.
- About 5.4 million BTC, roughly a quarter of supply, already sits in open outputs.

## Tools and manifesto

- [Schrödinger's Wallet](https://catbitcoin.com/schrodingers-wallet-checker/)
- [Closed vs open](https://catbitcoin.com/closed-vs-open-bitcoin-addresses/)
- [Why the cat](https://catbitcoin.com/why-cats-and-schrodinger/)
- [Address reuse](https://catbitcoin.com/address-reuse-opens-the-box/)
- [Already-open: P2PK](https://catbitcoin.com/already-open-addresses-p2pk/)
- [How an address labels the box](https://catbitcoin.com/what-is-a-bitcoin-address-explained/)
- [Which types stay closed](https://catbitcoin.com/bitcoin-address-types-explained/)
- [Hardware wallets](https://catbitcoin.com/hardware-wallets-and-the-box/)
- [Multisig](https://catbitcoin.com/multisig-and-quantum-risk/)
- [Change addresses](https://catbitcoin.com/change-addresses-open-the-box/)
- [xpub / watch-only](https://catbitcoin.com/xpub-watch-only-and-the-box/)
- [The key in the box](https://catbitcoin.com/what-is-a-public-key-vs-private-key/)

## Quantum cluster

- [Is Bitcoin safe today?](https://catbitcoin.com/is-bitcoin-safe-from-quantum-computers/) — yes
- [Shor's algorithm](https://catbitcoin.com/shors-algorithm-explained-for-bitcoin-holders/)
- [How many coins are open](https://catbitcoin.com/how-many-bitcoin-are-quantum-vulnerable/)
- [Taproot opens on arrival](https://catbitcoin.com/taproot-and-quantum-risk/)
- [Exchange custody](https://catbitcoin.com/is-my-exchange-account-safe-from-quantum/)
- [When, if ever](https://catbitcoin.com/when-will-quantum-computers-break-bitcoin/)
- [Move to a still-closed address](https://catbitcoin.com/how-to-move-bitcoin-to-a-safer-address/)
- [Later address types](https://catbitcoin.com/quantum-resistant-bitcoin-address-types/)
- [BIP-360](https://catbitcoin.com/what-is-bip-360-explained/) — draft, not consensus
- [Post-quantum cryptography](https://catbitcoin.com/post-quantum-cryptography-explained-simply/)
- [Other coins](https://catbitcoin.com/bitcoin-vs-other-cryptocurrencies-quantum-risk/)
- [Satoshi's coins](https://catbitcoin.com/what-happens-to-satoshis-coins/)

Retired (noindex): sats converter, halving explainer.

## Site

- [Home](https://catbitcoin.com/)
- [About](https://catbitcoin.com/about/)
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