Thread View: de.comp.sources.d
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Started by Stefan Scholl
Thu, 20 Aug 1992 18:12
Worm Crypt gesucht
Author: Stefan Scholl
Date: Thu, 20 Aug 1992 18:12
Date: Thu, 20 Aug 1992 18:12
38 lines
2280 bytes
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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