[cap-talk] Implementing a crypto brand: What are the security requirements?

[Pierre THIERRY]

Scribit David Wagner dies 22/03/2007 hora 21:05:
> > Confidentiality
> >     Without possession of Unsealer A, possession of a Box A does not
> >     yield any information about its contents.
> [...]
>
> You might think that no attacker who uses only the public interface
> getOne() can learn anything about the value of the boolean b.  But now
> consider this:
>     void attack() {
>         Box box;
>         {
>             Object o1 = new int[1] { 0 };
>             Object o2 = new int[1000000000] { 0 };
>             box = getOne(o1, o2);
>         }
> 
>         // wait for gc
> 
>         // test whether o2 has been garbage collected or not,
>         // e.g., by checking for cache effects or disk thrashing
>     }

But in this case, you gain information on the content with much more
than the box, because you have information on both:
- its internals (IIUC, your attack is meant to reveal the boolean, so
  you know it's there),
- the lexical scope of its creation, without which this particular
  attack is impossible

So maybe, at the light of this attack, the requirement could be
rephrased as:

  Confidentiality Without possession of Unsealer A, the sole possession
  of a Box A does not yield any information about its contents.

Precisely,
Pierre
-- 
nowhere.man at levallois.eu.org
OpenPGP 0xD9D50D8A
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