Private Key
A secret cryptographic number that proves ownership of a blockchain address and authorises transactions.
A private key is a 256-bit number generated randomly when you create a wallet. It is the master credential: whoever holds it controls all assets at the corresponding public address. Private keys should never be shared with anyone.
From the private key, a public key is derived using elliptic-curve cryptography, and from the public key, a public address is derived. The relationship is one-way — you cannot calculate a private key from a public key or address.
Most modern wallets represent private keys as a 12- or 24-word seed phrase (BIP-39), which is easier to write down and recover than a raw hex number. Keeping this phrase offline and physically secure is the single most important act of crypto self-custody.