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Thread View: de.comp.sources.d
1 messages
1 total messages Started by Stefan Scholl Thu, 20 Aug 1992 18:12
Worm Crypt gesucht
#15
Author: Stefan Scholl
Date: Thu, 20 Aug 1992 18:12
38 lines
2280 bytes
Ich suche den Source zu dem Crypt Algorithmus, zu dem folgende
Beschreibung passt:

-------------------------
INTERNET WORM CRYPT() ROUTINE
notes from 'Password Cracking: A Game of Wits' by Donn Seeley CACM,
June89 v32n6 pp700-703 : The Worm's crypt algorithm appears to be a
compramise between time	and space: the time needed to encrypt one
password guess verses the substantial extra table space	needed to
squeeze	performance out	of the algorithm...The traditional UNIX
algorithm stores each bit of the password in a byte, while the worms
algorithm packs	packs the bits into into two 32-bit words. This
permits	the worms algorithm to use bitfield and	shift operations on
the password data. (also saves a little	space!)
  Other	speedups include unrolling loops, combining tables,
precomputing shifts and	masks, and eliminating redundant initial and
final permutations when	performing the 25 applications of modified
DES that the password encryption algorithm uses.
  The biggest performance improvement comes from combining
permutations: the worm uses expanded arrays which are indexed by
groups of bits rather than single bits.
  Bishops DESZIP.c does	all these things and also precomputes more
functions yielding twice the performance of the	worms algorithm, but
requiring nearly 200KB of initialized data as opposed to the 6KB
used by	the worm, and the less than 2KB	used by	the normal crypt().
  The worms version of crypt ran 9 times faster	than the normal	crypt
while DESZIP runs about	20 time	faster (FDES + DESZIP are about
equivalent). on	a VAX 6800 encrypting 271 passwords it took the	worms
crypt less than	6 seconds or 45	passwords per sec, and the normal
crypt took 54 seconds or 5 passwords per second. - Tangent
cut here:
-------------------------


-- 
|From: Stefan Scholl <stesch@sks.ppc.sub.org>
"Yeaa, yeaa, yeaa, yeaa, yeaa, yeaa, yeaa!"   Nirvana
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