Re: Double Encryption Illegal?

Runu Knips wrote:
>
> Mok-Kong Shen wrote:
> > Tom St Denis wrote:
> > > Mok-Kong Shen <mok-kong.shen_at_t-online.de> wrote:
> > > > Tom St Denis wrote:
> > > > > pausch_at_saafNOSPAM.se (Paul Schlyter) wrote:
 

> > > > > > So you're claiming that triple-DES is no more secure than single-
> > > > > DES ???
> > > > >
> > > > > Read my message. Geez. I said "double" encryption is not the way
 to
> > > > > go about added security.
> > > >
> > > > Could you be more explicit and explain why? Are you
> > > > saying that superencipherment is always nonsense?
> > > > Is 2-DES not better than DES?
> > >
> > > Given sufficient memory 2-des is not better then des.
> >
> > Please exlpain your claim or refer to literature.
>
> That is the reason why people use 3DES, and never 2DES.
>
> Well this has been explained, for example, in Bruce Schneiers
> Applied Crypto. At least I think so ;-), I don't have it at
> hand in the moment. There is an attack which requires masses
> of memory, but then you can attack 2DES by attacking it from
> both ends (meet-in-the-middle-attack).

Do you really mean that a 2-DES (with two independent keys) is not an jota stronger than DES??

>
> It is also explained in my other crypto book, "Abendteuer
> Kryptologie" (Adventure Cryptology), by Reinhard Wobst,
> Addison Wesley, ISBN 3-8273-1413-5, page 192ff.

It is strange that I found p.192 of this book (1997 edition) deals with RC5 and not DES or 2-DES. I suppose you erred. Could you give the correct page number?

M. K. Shen Received on Mon Sep 18 2000 - 20:07:24 CEST