Public-key exposure
Whether an address's full public key is visible on-chain. Exposure matters because quantum risk to a wallet begins only once the public key is published — before that, an attacker sees just a hash.
In practice
An unspent P2PKH Bitcoin address publishes only HASH160 of the public key. The key itself appears on the first spend.
Related terms
Receiving funds repeatedly at an address that has already spent. Because the first spend publishes the public key, every later balance at that address sits behind an already-exposed key.
The legacy Bitcoin address type beginning with 1, which locks funds to the hash of a public key rather than the key itself. An unspent P2PKH output does not reveal its public key.
The signature scheme used by Bitcoin, Ethereum and most blockchains, based on elliptic curves such as secp256k1. It is not post-quantum: Shor's algorithm would recover the private key from an exposed public key.
A Bitcoin upgrade introducing bc1p addresses and Schnorr signatures. Taproot key-path spends place a public key in the output, so a funded Taproot address exposes a key earlier than a comparable P2PKH address.