Quiz no 1

[ancalagon]

Theodoros V. Kalamatianos wrote:
> On Wed, 7 Apr 2004, Jimmy Angelakos wrote:
> 
> 
>>Exm... de nomizw... den eimai sigouros alla apla CRC32 checksums den 
>>krataei? Se auth thn periprwsh den uparxei oute robustness oute tipota apo 
>>tis fantasiwseis sou :>
> 
Auto den ginotan pote
> 
> Vasika sta sxetika palia systhmata eixan ena DES derived hash gia kathe 
> password, i.e. ena kleidi twn 56 bit. Auto safws kai spaei sxetika eukola 
> pleon, akoma kai me aplous algorithmous pou dokimazoun olo to keyspace me 
> th seira. Den kserw omws an to "eukola" isxyei kai gia to PC tou spitiou 
> sou, afou den to exw dokimasei pote :-)
> 
Auto isxyei me tin e3is logiki: dinetai ena kleidi 8 xaraktiron apo to 
opoio lambanontai apo ta 64 mono ta 56bits. Katopin to keno keimeno ""
cryptografotan kata DES vasi tou kleidiou. Gia prosthiki polyplokotitas 
oste stin periptosi idion password se 2 diaforetikous accounts 
prostithetai ena tyxaio sinolo 2 xaraktiron (to legomeno salt). To salt
katopin topothetitai stin arxi tou kryptografimenou telika keimenou to
opoio einai panta 13 xaraktires kai grafetai sto arxeio.

Tin teleutaia fora pou ekana benchmarks se enan 500 celeron eixa giro 
sta 10000 accounts check/s me ena pragmatika athlio programmataki pou 
egrapsa mesa se 5 lepta.(kante pra3eis ean thelete. To epitrepto sinolo
xaraktiron gia kathe pass einai pantos gia sketa alphanumeric passes
[a-z],[A-Z],[0-9]). Profanos professional tools kai ta taxitera 
sistimata kanoun eukoloteri apo oti palia tin euresi ton passes. Eidika
gia ta apla pou akolouthoun xazous kanones styl username123,onomata
oikogeneias123,zoon123,xoron123 kai diafora alla tetoia spane mesa se 
deuterolepta me ta katallila ergaleia.

> Sta pio nea systhmata (p.x. linux distributions apo 2000 kai meta) 
> xrhsimopoioun ena MD5 hash twn 128bit. Auto einai sxetika dyskolo na 
> spasei. An ta passwords htan pragmatika tyxaia tote oi pithanothtes kai h 
> diarkeia ths anthrwpinhs zwhs einai mallon enantion sou. Wstoso edw o 
> adynamos krikos einai o anthrwpos, gi'auto kai oi kryptografikes 
> epitheseis me xrhsh leksikwn einai olo kai pio syxnes.
milame gia FreeBSD,kai Linux akomi kai prin to 2000 eno den thymamai ti 
ekane tote to NetBSD. O MD5 se antithesi me ton DES einai kanonikos
hashing algorithmos kai typika gia tin efarmogi pou mas noiazei auti tin 
stigmi aspastos se logiko xrono me e3antlitiki anazitisi(1000000 genies 
meta apo esena paizei na doun to pass). Gia auto to logo kai ginontai oi
epitheseis me xrhsh leksikon pou den einai olo kai pio syxnes alla o 
kanonas.

Pantos ena account poly pio eukola diareei apo kapoia blakeia tou 
anthropou pou to anikei para logo tis apothikeuseis tou, an kai panta 
yparxei auti i pithanotita.