Changing preferences

[David Shaw]

On Mon, Sep 22, 2008 at 02:37:17AM -0500, Robert J. Hansen wrote:
> Faramir wrote:
> >> No, but they may be operating on the assumption their preference list
> >> matters.  (Which it very often doesn't; encrypting-to-self and another
> >> recipient means there's a 50/50 chance their preference list will be
> >> treated as a cap set.  It would appear this ought to be made clear in
> >> the docs.)
> > 
> >   What do you mean? I didn't understand the "cap set" concept, or at
> > least, the meaning of these words (I think probably is due my lack of
> > vocabulary...).
> 
> Imagine a group of people are going to the movies.
> 
> "I'd like to see either _Iron Man_, _The Incredible Hulk_, or _The Dark
> Knight_."
> 
> Compare to:
> 
> "I'd like to see _The Incredible Hulk_.  If that's not possible, I'd
> like to see _The Dark Knight_.  If neither of them are possible, I'd
> like to see _Iron Man_."
> 
> The first one says "I'd like to see any of these movies and I don't care
> which we choose."  This is a capability set.
> 
> The second one says "while I'll watch any of them, I would prefer _The
> Incredible Hulk_."  This is a preference list.

Good analogy.  I usually explain it with pizza toppings ("I like
pepperoni or mushrooms, but hate anchovies").  3DES is then the plain
cheese pizza that everyone can settle on if they have to.

David