BIND Configuration File Guide--key Statement

key key_id {
  algorithm algorithm_id;
  secret secret_string;
};

The key statement defines a key ID which can be used in a server statement to associate an authentication method with a particular name server.

A key ID must be created with the key statement before it can be used in a server definition.

The algorithm_id is a string that specifies a security/authentication algorithm. secret_string is the secret to be used by the algorithm.

The key statement is intended for future use by the server. It is checked for syntax but is otherwise ignored.