# Class type Http_client.key_handler

    class type key_handler = object .. end

    method inquire_key : domain:string list -> realms:string list -> auth:string -> key

The method is called when a new session must be authenticated. The `domain` is the URI list describing the protection space. URIs currently have the form "http://host:port/path", i.e. the port is always written out. The `realms` parameter is a list of realm identifiers. In `auth` the name of the authentication method is passed (lowercase characters). The method must search (or query for) a key, and return it. The key must refer to one of the passed realms. The domain of the key must be exactly the same as the passed `domain`. If the method raises `Not_found`, authentication will fail.

    method invalidate_key : key -> unit

The handler is notified that authentication failed for this key