[Bug 877] ssh 3.8.1p1 client cannot disable encryption with "-c none"

bugzilla-daemon at mindrot.org bugzilla-daemon at mindrot.org
Tue Jun 8 17:25:06 EST 2004


------- Additional Comments From mohit_aron at hotmail.com  2004-06-08 17:25 -------

Based on the patch that Markus had posted for implementing the "none" cipher and
mac, here is some data I've collected.

I did a transfer of 4 MB from my office machine to my home machine. The transfer
was done using scp over a VPN connection established between my home and office
machine. I did several transfers, varying the cipher and mac for each one. 
Each transfer was able to saturate the bandwidth available to me at the time (by
my Comcast broadband connection) of about 110 KBps. Thus, what's relevant is
the CPU ovhd. My home machine is a 800 MHz IBM T21 thinkpad running cygwin over
Windows 2000, while my office machine is a fancy 2.7 GHz machine running Redhat 
9. Here is the data from my home machine when the transfers were done (CPU was
consistently 82% idle when no transfer is being done):

Cipher          MAC            CPU idle

default         default        55%
arcfour         default        60%
arcfour         none           60%
none            default        65%
none            none           65%

So it appears that disabling the MAC isn't giving me any benefits - or else
the patch doesn't quite disable the MAC.

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