NODE f1608ce2the key of DES
yjkim@ssrnet.snu.ac.kr (Kim Yoonjeong)Mon, 30 Sep 1996 22:04:26 +0800
Hello, all !
With given a unknown DES system with 64 bits plaintext p, ciphertext c,
can there be MORE THAN ONE keys ?
If so, How is the probability (big or small)?
Sincerely,
- Yoonejong
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Yoonjeong Kim Email: yjkim@ssrnet.snu.ac.kr
Department of Computer Engineering Phone: +82-2-875-7726 (office)
Seoul National University +82-2-872-9801 (home)
Seoul 151-742 Korea Fax: +82-2-875-7726
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
NODE 3957e6d5Re: the key of DES
The Deviant <deviant@pooh-corner.com>Tue, 1 Oct 1996 08:00:44 +0800
On Mon, 30 Sep 1996, Kim Yoonjeong wrote:
> Hello, all !
> With given a unknown DES system with 64 bits plaintext p, ciphertext c,
> can there be MORE THAN ONE keys ?
No.
> If so, How is the probability (big or small)?
>
> Sincerely,
> - Yoonejong
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> Yoonjeong Kim Email: yjkim@ssrnet.snu.ac.kr
> Department of Computer Engineering Phone: +82-2-875-7726 (office)
> Seoul National University +82-2-872-9801 (home)
> Seoul 151-742 Korea Fax: +82-2-875-7726
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>
>
>
--Deviant
"If you eliminate the impossible, whatever remains, however improbable,
must be true." -- Spock
NODE 60940367Re: the key of DES
"I~nigo Gonzalez" <nexus@adv.es>Wed, 2 Oct 1996 09:32:42 +0800
Kim Yoonjeong wrote:
>
> Hello, all !
> With given a unknown DES system with 64 bits plaintext p, ciphertext c,
> can there be MORE THAN ONE keys ?
I don't think so:
I you look closely to 1-Round DES, you can have this case:
Let p=LR (plaintext) and K=key (without parity check)
When computing f(R,k) in 1-Round DES I can have the same
input (and output) in the S-Boxes with:
p=LR, with k ; and p=L(R'), with k'
(k' denotes 1-complement of k)
You have _two_ different (plaintext,key) pairs with
the same input using f(R,k) and f(R',k').
>From this, you can prove that:
if y=DES(p,k) then y'=DES(p',k')
wich is what everyone really wants: a beautiful chance of using
a trapdoor in DES.
Did you like it? - Don't use DES: It's not reliable.
--
Iñigo González - ADV Internet Technical Advisor <nexus@adv.es>
"Never say anything online that you wouldn't want to see on the
front page of The New York Times." - alt.2600.moderated Posting