[436] in Kerberos_V5_Development
Re: Kerberized Telnet
prb@ATHENA.MIT.EDU (prb@ATHENA.MIT.EDU)
Thu Nov 15 22:55:43 1990
Telnet and rlogin have different encryption mechanisms. I have been told
that rlogin encrypted each character and sent over 8 times as much data.
Telnet does not do that. It XORs in data genereated using DES feedback
on a random inital feed (known to both sides) so that no more data is
sent accross encrypted than in the clear. Also, a des_ecb_encrypt()
is only called for each 8 characters sent (called for the first character
and then there is data for the next 7). I have not noticed any
slugishness when in encrypted mode.
But I have done some more timings, this time looking at CPU time instead
of Real time. Turns out that the System time stays the same (no surpise
there) but the user time increases by 328% (user + system increases by
about 200%). I was timing telnet on my SPARC to get these numbers.
My conclusion: On a system with few users (perhaps one) it really
doesn't make a difference, but on a timeshare system with many users
using telnet, it could have an impact on system performance.
PS: Sorry about formatting problems, I am using the TTY interface
and don't know how to go back and edit (spelling mistakes too)
