SilcAsyncOperation
    silc_connauth_initiator(SilcConnAuth connauth,
                            SilcConnectionType conn_type,
                            SilcAuthMethod auth_method, void *auth_data,
                            SilcUInt32 auth_data_len,
                            SilcConnAuthCompletion completion,
                            void *context);

    Starts the connection authentication protocol as initiator.  The
    `conn_type' is the type of connection we are.  The `auth_method' is
    the authentication method.  If it is SILC_AUTH_PASSWORD the `auth_data'
    and `auth_data_len' is the passphrase and its length, respectively.
    If it is SILC_AUTH_PUBLIC_KEY the `auth_data' is the SilcPrivateKey
    used to produce the digital signature.  The `auth_data_len' is 0.
    The `completion' with `context' will be called after the protocol
    has completed.

    This returns SilcAsyncOperation context which can be used to abort
    the protocol before it is completed.  Returns NULL on error.