[cap-talk] "Ambient capability"

[Toby Murray]

On Mon, 2009-07-13 at 12:45 -0400, Sandro Magi wrote:
> Toby Murray wrote:
> > I also suspect we have a more precise meaning with some of the
> > terminology we use. In particular, Dmbarbour's use of the word
> > "capability" appears to be more inline with the everyday use of the term
> > along the lines of "ability" or "power". 
> >
> > Some of the discussion on the erights wiki has involved making
> > distinctions between "secure" and "insecure" capabilities, namely ones
> > that cannot and can be forged respectively. In this sense, there is no
> > such thing as an insecure capability in a capability-based system,
> > including all object-capability systems.
> 
> I don't think so. dmbarbour added the "secure" modifier to "capability"
> once, when referring to object capabilities, and such a modifier does
> not inherently change its meaning; he never mentioned "insecure"
> capabilities. You might consider the use of the modifier as implying a
> belief in "insecure" capabilities, but he never mentioned such a thing
> explicitly, so I'm not sure that's a fair inference; there was also no
> discussion of forgery that I saw, beyond mention that capabilities are
> unforgeable.

See the talk page for Capability
http://wiki.erights.org/wiki/Talk:Capability. In particular, the
following from Dmbarbour in response to Kosic:

"I'm afraid you didn't grok. I mean to say that capabilities may be very
forgeable and guessable. They [the forgeable and guessable capabilities]
simply aren't secure capabilities, or suitable for capability-based
security. And the page still has a heavily object-capability bias."

This clearly implies some meaning to the word capability (as a noun)
that has room for ones that "aren't secure" (i.e. "insecure" ones)
outside of the scope of "capability-based security

I wasn't implying Dmbarbour does not understand capabilities nor
capability-based security. Merely that his/her writings seemed to be
using the word "capability" in a more broad sense than would be ideal
for the rights wiki IMO.

Cheers

Toby