Re: Nortel CES (3DES version) offers false sense of securitywhen usi ng IPSEC

[Rogier Wolff <R.E.Wolff () BITWIZARD NL>]

MCKILLICAN, DONALD wrote:
> Rogier Wolff wrote:
>
> > I don't know where people get their information, but tripple-DES uses a 112
> > bit key. How they can advertize 128, or even 168 bits of keys I don't know.
>
> In fact, there are a number of different modes for TripleDES.  Some of them
> use one key, some of them use two, and some use three.  A commonly used
> example of the last named is DES-EDE3.
>
> See, for instance,
> <http://www.crypto.nkfurst.edu.tw/infosec/faq/html/3-2-6.html> for more
                        ^^^ remove that R in the URL.
> precise explanations.

Still, I remember that using triple-DES with three keys only had a
complexity on the order of 2^112. No matter what you tried.

Sure you can design super-duper-crypto scheme that uses a gigantic
key, but as long as the resulting crypto only has 2^56 complexity to
break, it doesn't have any real advantages over, say, DES.

Anyway, I can't quickly find any hard online references to back this
up.

http://www.rsasecurity.com/rsalabs/faq/3-2-6.html

hints at a possible problem:

     The use of double and triple encryption does not always provide
     the additional security that might be expected.

So: I claim that I heard that "all triple-DES keying with three keys
have complexity of 2^112 or less. It gives only a false sense of
security if you key your triple-des with more than 112 bits".

RSA partially backs me up by saying that SOME triple-DES methods are
of a lower complexity than what might be expected from the raw
keysize.

Note that searching for "triple DES" on the net leads to plenty of
references, wich claim for instance 192 bits of keyspace, showing a
fundamental misunderstanding with DES.

                                Roger.

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