Finding encrytion algorithm

gfgs pedo jtrjtrjtr2001 at yahoo.com
Sat Jul 13 09:39:36 PDT 2002


hi,

thanx for the replies.
one doubt escpecially on this.
>
>But every algorithm has some 
>statistical
>signature and if you've got enough cipher text you
>can compare that
>signature with known algorithms to home in on fewer
>choices.

can u pls explain how they have statistical
signatures,pls-


 may be using SPN's, i have tried ANSI X9.17 key
generation with GOST-it did have a negligably small
skew-it makes me wonder what statistical signature
they have.The negligable skew is a weakness but not
high enough to compramise the security of the key used
from the ANSI x9.17 key gen method.
pls explain.
thank u veru much.

Regards Data.




--- Mike Rosing <eresrch at eskimo.com> wrote:
> On Thu, 11 Jul 2002, gfgs pedo wrote:
> 
> > suppose a cryptanalysis only has encrypted
> data-how is
> > going 2 know which is the encrytion algorithm used
> 2
> > encrypt the data ,so that he can effeciently
> > cryptanalyse if
> >
> > 1:>he has large amount of cipher text only
> > 2:>has large amount of plain text and
> corresponding
> > cipher text.
> >
> > There r so many encryption algorithms,how does he
> know
> > which algorithm was used?
> 
> Depends on how they got the source.  They may know
> it's one of 5
> possible choices because of the person who sent (or
> received) it.
> If it's just found on a disk in a garbage dump with
> no connections
> to anyone, it's a bit tougher.  But every algorithm
> has some statistical
> signature and if you've got enough cipher text you
> can compare that
> signature with known algorithms to home in on fewer
> choices.
> 
> I'm not sure having the plaintext helps much more,
> but you could
> use random keys to create several ciphertexts with
> known algorithms and
> compare the statistics just to see if they compare
> better.
> 
> It's definitly challenging :-)
> 
> Patience, persistence, truth,
> Dr. mike
> 
> 


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