A private key is secret cryptographic data used to create digital signatures that authorize transactions or prove control of blockchain credentials.
Public-key cryptography links a private key to a corresponding public key. Blockchain systems use digital signatures to verify that a transaction was authorized by the party controlling the relevant private key or signing scheme. Wallet software usually handles this process without exposing the raw key to the user. If a private key is lost and no recovery mechanism exists, the user can lose the ability to authorize transactions from the associated assets.
The private key authorizes signatures. The public key is used in signature verification and, in many blockchain systems, contributes to the derivation of addresses.
Private-key security is central to self-custody because unauthorized access can allow irreversible transfers, while permanent loss can make assets inaccessible.
A wallet can sign a stablecoin transfer locally with a private key and send the signed transaction to the network for verification.