Yet Another useful paper

[David L. Jobusch]

In article <1273 at altger.UUCP> vyrus at altger.UUCP (vyrus) writes:
>I have heard about a paper presenting a mathematical formulation of a fast
>implementation of the DES in software able of speding up UNIX crypt()
>password encryption routine by roughtly 20 times. (@ulysses.homer.nj.att.com)
>
>I wonder if someone would mind telling more about the matter or, (even better!)
>sending me an high language (C? great!) implementation of such algorithm.
>
>Thanks in advance.
>
>=David=

Well, I suspect one way you might be able to "speed up" UNIX crypt() is
to remove the following two lines from the code in 4.3BSD crpyt.c/crypt():
	
	for(i=0; i<25; i++)
		encrypt(block,0);
	
Looking at the code, each 64-bit block is encrypted 25 times.
( encrypt() takes "block", encrypts it, and returns it in "block".) 

Besides the intention of making crypt slow in the first place, does anyone 
have comments on the usefullness of multiple encryption of blocks? I have
heard some arguments that doubt multiple encryption increases protection
against the bad guy.

Also, I have what seems to be a very quick implementation of DES written
in 'C' that was posted to UseNet some time ago. Interested individuals
can contact me email at:

Dave Jobusch
Iowa State University Telecommunications
Ames, IA
jobusch at atanasoff.cs.iastate.edu