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Re: Findes et os pop3 system, der er let at administrere og som er sikkert?



Jacob Bunk Nielsen <sslug@sslug> writes:

> Arne Jørgensen <sslug@sslug> writes:
>> Jacob Bunk Nielsen <sslug@sslug> writes:
>>
>>> så laver man 3DES ved: c = e(d(e(x),k3), k2), k1).
>>
>> I flg. Tannenbaum, "Computer Networks", 4. udgave, s. 740 er k1=k3 i
>> 3DES.
>
> Jeg kan desværre ikke lige finde noget bedre end Handbook of Applied
> Cryptography, som siger at man *kan* bruge 2-nøgle 3DES, men at man
> ikke nødvendigvis behøver at gøre det. Den er dog ret svag i sine
> formuleringer om emnet.

Efter selv at have surfet på emnet ser det ud som at der retteligt
findes tre varianter af 3DES, altså k1!=k2!=3, k1=k3 og k1=k2=k3.

Og efter en nærlæsning af ovennævnte Tanenbaum er han lidt ulden i
formuleringen "The method chosen ..." som ikke er præcis mht om det er
den metode han har valgt at vise i bogen eller den metode man har
valgt som erstatning for DES ...

Han skriver i øvrigt at den er standardiseret i ISO 8732. Hvilken
version af 3DES det så er må stå hen i det uvisse ... ISO-standarder
er jo ikke så nemme at få fingerene i.

> <http://kingkong.me.berkeley.edu/~kenneth/courses/sims250/des.html>
> siger at du har ret.
>
> Jeg må indrømme at jeg ikke husker godt nok til at huske hvad min
> underviser i "kryptologi"-kurset sagde om emnet.

Bare rolig. Jeg er overhovedet ikke ekspert på området!

mvh
        /arne
-- 
Arne Jørgensen <http://arnested.dk/>


 
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