identd on a masq gateway, answering with hostnames?

Hi! For a masquerading gw allowing internet access to authenticated users, I need an identd that answers ident-requests giving the (hashed) hostname and user-id of the client that connected to the requesting system. This is to make sure that in case of abuse, the responsible can be found and the admin of the gateway is not made responsible (as the connections come from the gateway ip address as seen from the server). I could provide the identd with the information which local ip (which will be masqued to the outside) belongs to which user. All that is some kind of an extension to an authenticating gateway. Is anyone using something like that, or does anyone know a solution? TIA, CU Lars.