Re: [GNU Crypto] how to deal with weak keys. was: Documentation

[Raif S. Naffah]

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hello Casey,

On Thu, 29 May 2003 05:00 am, Casey Marshall wrote:
> On Thu, May 29, 2003 at 04:17:36AM +1000, Raif S. Naffah wrote:
> > On Thu, 29 May 2003 02:47 am, Casey Marshall wrote:
> > > On Wed, May 28, 2003 at 08:29:15PM +1000, Raif S. Naffah wrote:
> > > > ok.  i see the benefit of allowing even weak keys to go through
> > > > the implementation.  i double checked all the FIPS publications
> > > > relevant to DES, and couldnt find even a warning about weak
> > > > keys!
> > > >
> > > > here is what i propose; it's similar to what we already do in
> > > > the PRNG class: use of conditional compilation.
> > > >
> > > > * add in each cipher implementation which is known to exhibit
> > > > weak, or semi-weak keys, a private static final boolean
> > > > CHECK_WEAK_KEYS with a default value.  in the makeKey() method
> > > > we add the code to check for weak keys conditioned by the value
> > > > of CHECK_WEAK_KEYS.
> > > >
> > > > * in the code, distinguish the case of weak keys with a new
> > > > exception that is a subclass of InvalidKeyException.  this way
> > > > the code will remain backward compatible.
> > > >
> > > > * add a warning in the documentation, incl. the README about
> > > > the set default for CHECK_WEAK_KEYS, and how the user can
> > > > change it to get the desired effect if it is not set to the
> > > > appropriate value.
> > > >
> > > > how does this sound?
> > >
> > > I like the idea of making the check optional, but how about
> > > making this a property? Perhaps in a global, static property set,
> > > somewhat akin to the properties contained in
> > > java.security.Security?
> >
> > excellent!  we should probably move all similar flags to there too.
> > would the Registry be an appropriate place for this?
>
> It would probably be more appropriate to have a class in gnu.crypto
> that contains static methods such as set/getProperty, so we can use a
> PropertyPermission check before querying/setting these (sometimes
> sensitive) properties.

if we do that we lose the conditional compilation benefit.  for 
performance reasons mostly, and security secondly i'd rather have them 
as static finals.


> IMHO, of course.

- -- 
cheers;
rsn
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