[Jsdsi-devel] circular proofs

[Sameer A. <aj...@cs...>]

>> > 5. A class to detect circular questions.
>> Like "Does Alice grant read access to Alice"?
>
> No. More when:
> Alice grants read to Bob
> Bob grants read to Carol
> Carol grants read to Alice
>
> And you then ask to Prove that Derek can read - it prevents the Prover
> (and Searcher) going round in a circular reference). Works by each
> Pipeline having a CircularQuestionDetector which keeps track of recent
> questions and throwing an exception if one re-appears.

Are you sure the Prover goes around this repeatedly?  It's designed to
handle this case cleanly: before it inserts a new certificate, it first
checks whether it has already seen that certificate.  This way, the Prover
is guaranteed to stop when all possible certificate compositions are done.

I have just checked in a CertPathTest that exercises this behavior.  In
input certificate set is defined in the file certs.in.5:

ALICE +read -> BOB
BOB +read -> CAROL
CAROL +read -> ALICE

The output file certs.out.5 contains all of the certifcates that the
Prover found:

ALICE +read -> ALICE
ALICE +read -> BOB
ALICE +read -> CAROL
BOB +read -> ALICE
BOB +read -> BOB
BOB +read -> CAROL
CAROL +read -> ALICE
CAROL +read -> BOB
CAROL +read -> CAROL

The prover does in fact terminate, so I believe it works okay with
circular cert sets.  Can you create a test that fails?

Sameer