[cap-talk] Why is EQ so dang fascinating?

[Jed Donnelley]

On 10/20/2007 12:31 PM, Dean Tribble wrote:
...
> The real question: why is EQ so dang fascinating?...

Isn't this because EQ is the one primitive that seems
to need to exist besides "invoke"?  If we didn't need
to have EQ then all operations would be extendable
and emulatable (the "insertion" property) and the
TCB reduced (though perhaps trivially).  If we argue
that all authority must be granted by capability,
what capability is it that grants EQ?

With EQ I can't completely emulate a capability
(insure that it can't be distinguished by EQ and
thus potentially change function).  E.g. a
program might ask, is this the 'real' capability
or is it an impostor (e.g. a membraned version
that might be revoked at a later time).  With EQ
I can find out and potentially change my behavior.
Without EQ I can't find out and the emulation
(e.g. a membrane) can be more complete.

If there is more or less to the fascination with
EQ, I'd like to hear it.

--Jed  http://www.webstart.com/jed/