bounded storage model - why is R organized as 2-d array?

[Steven M. Bellovin]

On Thu, 09 Mar 2006 02:10:58 -0500
alex at alten.org wrote:

> This is very useful for encrypting things like video 
> streams without an expensive hardware cryptographic accelerator card.
> 
I think you vastly overestimate how much hardware one needs to do
something like AES.  I ran

  	dd if=/dev/zero bs=32k count=1024| openssl speed aes-128-cbc

on a 1500 Mhz Athlon.  It reported speeds of ~27.5 MBps, or 220 Mbps.
Even video isn't that fast, and that's a slow CPU by today's standards.

Also -- I don't know how large these random tables have to be, but if
they don't fit in cache the cipher will be quite slow -- memory
bandwidth hasn't increased nearly as rapidly as CPU speed; modern
machines utterly rely on their caches.

		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb

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