What is a public key?
The partner of a private key. It lets anyone check a signature without revealing the private key under current computing assumptions.
Not to be confused with: your private keyPrivate keyThe secret number that lets you spend your bitcoin. Whoever knows it controls the coins, so it must never be shared., your addressAddressA string of letters and numbers that tells someone where to send you bitcoin, a bit like an account number for one payment..
Your public key is made from your private keyPrivate keyThe secret number that lets you spend your bitcoin. Whoever knows it controls the coins, so it must never be shared. with one-way maths on an elliptic curveElliptic curve (secp256k1)The curve y² = x³ + 7, whose maths turns a private key into a public key that ordinary computers cannot reverse efficiently.. No known ordinary-computer method can reverse it efficiently; in theory, a large enough quantum computerQuantum computer (qubit)A computer that uses quantum physics to solve some problems far faster than ordinary ones. Its working parts are called qubits. could.
Legacy and SegWitSegWitSegregated Witness: a 2017 upgrade that moved signatures into a separate part of each payment, making room for more payments. v0 addresses generally show a fingerprint until a spend reveals the key, including while that spend is unconfirmed. TaprootTaprootA 2021 upgrade that added Schnorr signatures and addresses starting bc1p, making complex payments cheaper and more private. addresses include an output public key from the start.
References
- Bitcoin Improvement Proposals, “BIP-341: Taproot: SegWit version 1 spending rules”.