Re: [zcap-spec] Request for Clarification (Is it "what" or "why?" and cross-matching)

On Sun, Mar 5, 2023 at 7:27 PM Alan Karp <alanhkarp@gmail.com> wrote:
> Pardon me for butting in, but I've been using capabilities since 1996 and may be able to clarify some things.

Bob, closing the loop on this... I didn't respond because I was hoping
that Alan would, and do a far better job than I in boiling the
conversation down to first principles.

Yes, everything Alan said.

* A capability designates a resource (FILE-X) and a permission that
acts on that resource (READ).

* You exchange one or more VCs (that prove that you should be allowed
to take a particular action on a particular resource) for a capability
(that allows you to take a specific action on a specific resource,
including delegating the capability to some other entity, possibly
with further restrictions).

People will debate the second point, noting it's unnecessary. While
that might be technically true, if you do that, you stand a good
chance of putting your system into a confused deputy situation. The
people that argue against combining VCs w/ Capabilities are concerned
about proper layering of security primitives. Those that argue for
expressing capabilities as VCs, are just wrong! *ducks* :P

-- manu

PS: There's gotta be some sort of "Internet Law of Capability
Discussions" where, if there is any confusion around what capabilities
are and are not, that Alan will eventually appear and deftly untangle
the conversation. :P

-- 
Manu Sporny - https://www.linkedin.com/in/manusporny/
Founder/CEO - Digital Bazaar, Inc.
News: Digital Bazaar Announces New Case Studies (2021)
https://www.digitalbazaar.com/

Received on Monday, 13 March 2023 13:59:45 UTC