Re: lug-bg: crypto-api cipher ?

[vlk@email.domain.hidden (Vesselin Kolev)]

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"Bug" da se chete v kavichki... da go narechem slabost. Prichinata e, che
originalnia DES razraboten ot IBM e s mnogo malka dylzhina na
kliucha - 56 bita. Makar, che predi DES e bil officialen symetrichen crypto
algorithm v USA i Canada

FIPS PUB 46 "Data Encryption Standard" - jan 1977
ANSI - Data Encryption Algorithm - 1981

algoritymyt e neistoichniv kakto na diferencialen cryptoanaliz, taka i na
known plain text attack (osobeno lesno, ako informaciata predi kodirane
ne e bila kompresirana). Neustoichiv e na brute force ataka s 
paralelizacia na zadachata. Za primer vizh proektiranata ot Paul 
Kocher mashina za hardware-no vzlomiavane na DES spechelila 
premiata na RSA Data Security:

http://www.cryptography.com/resources/whitepapers/DES.html

Izvestni sa niakoi modifikacii na DES: GDES- Generalizaed DES i
CRYPT(3) koito se izpolzva za cryptirane na parolite v UNIX predi
vyvezhdaneto na MD5 heshovete. DES-X e drug variant na DES.

3DES ili TripleDES e prosto DES prilozhen 3 pyti i e kato krypka za
DES kato celta e da se uzpolzva trikratno kodirane:

Encrypt->Decrypt->Encrypt

3DES ne e nisho drugo osven prosto 3-kratno razshiravane na DES
s cel izbiagavane na slabostta na 56-bitovia kliuch. 3DES e baven
i ne se preporychva za izpolzvane v prilozhenia, koito celiat
proizvoditelnost. Toi e blokov chiper, chete informaciata na blokove
ot po 64 bita i kodira na praktika sys 168 bitov kliuch.

T.e. priemete izvineniata mi za nepostavianeto na kavichki okolo
dumata byg.!

    Pozdravi
     Vesselin Kolev
  
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