what do we call a key that is needed to claim ownership of an account, is stored and managed by blockchain users, and must not be leaked or lost

The key that is needed to claim ownership of an account, is stored and managed by blockchain users, and must not be leaked or lost is called a private key. Private keys are used in cryptography and cryptocurrency to authorize transactions and prove ownership of a blockchain asset. They are a large alphanumeric code with hundreds of digits and represent the final control and ownership of cryptocurrency. If private keys are stolen or lost, the crypto assets associated with them are also lost. Private keys are necessary to prove ownership of wallet addresses. To prove ownership of crypto assets, the most reliable way is to sign a specified message with the private key.