SilcBool
    silc_identifier_check(const unsigned char *identifier,
                          SilcUInt32 identifier_len,
                          SilcStringEncoding identifier_encoding,
                          SilcUInt32 max_allowed_length);

    Checks that the 'identifier' string is valid identifier string
    and does not contain any unassigned or prohibited character.  This
    function is used to check for valid nicknames, server names,
    usernames, hostnames, service names, algorithm names, other security
    property names, and SILC Public Key name.

    If the 'max_allowed_length' is non-zero the identifier cannot be
    longer than that, and NULL is returned if it is.  If zero (0), no
    length limit exist.  For nicknames the max length must be 128 bytes.
    Other identifiers has no default limit, but application may choose
    one anyway.

    Returns TRUE if the string is valid and FALSE if it is prohibited.