• key {Object | string | Buffer}
      • key: {string | Buffer} The key material, either in PEM or DER format.
      • format: {string} Must be 'pem' or 'der'. Default: 'pem'.
      • type: {string} Must be 'pkcs1', 'pkcs8' or 'sec1'. This option is required only if the format is 'der' and ignored if it is 'pem'.
      • passphrase: {string | Buffer} The passphrase to use for decryption.
    • Returns: {KeyObject}

    Creates and returns a new key object containing a private key. If key is a string or Buffer, format is assumed to be 'pem'; otherwise, key must be an object with the properties described above.

    If the private key is encrypted, a passphrase must be specified. The length of the passphrase is limited to 1024 bytes.