Supose you opened up a socket on the local machine. And that you ran your usual telnet to connect to it. The program listening on the local socket would be responsible for running one end of a 'LINK' like secure protocol. It would connect to either the remote telnet socket, or a special purpose socket at the remote end. There either you can use a pipe to a pty (standard telnet -> login shell -> LINK -> pty), or in a special socket through LINK out the telnet socket. (There is an obvious extention with multiple hops through LINK-socket programs which should provide the same kind of anonymity that is provided by the CP remailers.)
This is the kind of thing which is just perfect for a streams-based tty/networking environment. Create a streams module that implements Link and DH key excng. Push it on your tty stream at both ends. Works over modems, telnet/rlogin, what-have-you. A similar module could be created to sit below the IP module in SVRx-based Un*xes.
It is also likely to be obsoleted as soon as secure-ip gets out.
And once the vendors for both endpoints update to it. Could be a while.
Infact it would be nice to see some socket (perhaps 32?) become the standard for the secure telnet service.
I think it would be much better to develop something that will work with the current port numbers, else we stand a good chance of asking for a 'new' secure port foreach well-known service. (Secure SMTP, Secure ftp-cmd, secure ftp-data,...) Jim