[cap-talk] Capabilities for immutable data

[David-Sarah Hopwood]

On 2011-02-17 17:32, Sandro Magi wrote:
> There is a small debate happening over at LtU about the fundamentals of
> capabilities, and what it means to be a capability [1]. I know there has
> been considerable debate on this before, so I want to focus on one
> specific issue with specific examples: whether a reference to immutable
> data with an access control policy should be considered a capability.

If it has an access control policy -- i.e. you can't unconditionally access
the immutable data -- then you don't have a reference to the actual data,
only to a wrapper. For example, let's say the wrapper will only give you
the data if you pass in a token value, or will only encrypt using the
data as key. In those cases I'd say that the reference to the wrapper is
certainly a capability, because the wrapper has the authority to read the
data, which is not ambiently available. (That is, it isn't public data.)

-- 
David-Sarah Hopwood  ⚥  http://davidsarah.livejournal.com

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