I think that there are 2 different issues here.
1. PBKDF1 (and similar) algorithms (such as the one used by Kerberos - ISTR
this is a different way of doing the same thing) are really designed at
producing a good quality key with minimal entropy. The idea being that a
simple brute-force attack on the whole key space is not 'short-cuttable'.
Whilst they may be successful in achieving that objective, they will not help
if the user selecting the password chooses a weak example, such as a
dictionary word, car registration number or similar. (I know that you made
the caveat about 'usual precautions', but the reality is that these are
2. 56 bit DES tends to be dismissed as 'too weak'. Well, I don't know if
you have any knowledge of anybody ever having any DES-encrypted data
compromised by a brute force attack - I certainly don't. [password guessing,
on the other hand, is sadly familiar]. As you say, a couple of PC's are not
going to help much when it comes to attempting a brute-force attack on a
56-bit DES encryption. I think it is a shame that it has become received
wisdom that anything with a key length < 128 bits is bad. For your average
man in the street, 56-bit DES is perfectly adequate and likely to remain so
for a few years yet. (I had this problem a few days ago when trying to
explain to a company that using plain DES to support Windows/UNIX integration
using Kerberos was OK). They just did not accept it! Why, because they had
seen a TV programme where some pundit had explained that <128-bit == BAD
On Tuesday 06 July 2004 15:49, Manuel Kasper wrote:
> On 06.07.2004 15:25 +0100, Peter Curran wrote:
> > I think encyrption is intriguing as a solution to the
> > confidentiality issues, but as they are using DES on the Netgear
> > stuff I assume that you have to pre-configure all the devices with
> > a shared key. As this tends to be derived from a passord it could
> > be relatively easy to attack.
> I did a little analysis of HomePlug powerline networking about a year
> ago. The password hashing is done as per PBKDF1 - it involves using
> MD5 1000 times, so with the usual password precautions in place, the
> resulting 56-bit DES key should be good. Also, provided that the
> implementation in HomePlug doesn't suffer from similar flaws as WEP,
> 56-bit encryption is IMHO enough for home users. I mean, it's not
> like you can brute-force-search a 56-bit key in a useful amount of
> time with only a few PCs at hand...
> - Manuel
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