On Thu, 16 Oct 2008, Sudarshan Soma wrote:

> HI ,
> I have telnet server implemented on the server. Now i want the ssh
> client to connect to this modified telnet server by adding
> encryption/decryption functions in it.
> Can I do this easily by just putting the appropriate encrypt/decrypt
> functions , session key establishment code from ssh server to telnet
> server.
> Tunelling is one solution , i can think of . Is there any other easy
> alternative for this apart from changing the telnet server code.

It is not a trivial thing to add encryption to the telnet protocol. It
would have to be added on both ends (client and server), and it was not
widely done. One approach was called SRP, from Stanford University. I
haven't heard anything from them for a long time, since SSH became common.

Other ideas:

1. Use telnet with SSL. I have heard that there are SSL implementations of
the client and server sides of telnet, but I have not worked with them.

2. Use SSH to establish a secure connection to a) the same server, or b)
one nearby, inside the site's firewall. Establish client-side tunnelling
on port 23. Then on the client machine, telnet to localhost, so that it is
tunnelled to the server.

This can be useful for Windows-based server-side systems that accept
telnet connections but not SSH connections. I have even considered adding
a special telnet-over-ssh mode for our terminal emulation client, Anzio.

.....Bob Rasmussen, President, Rasmussen Software, Inc.

personal e-mail: ras@anzio.com
company e-mail: rsi@anzio.com
voice: (US) 503-624-0360 (9:00-6:00 Pacific Time)
fax: (US) 503-624-0760
web: http://www.anzio.com
street address: Rasmussen Software, Inc.
10240 SW Nimbus, Suite L9
Portland, OR 97223 USA