In this paper, we consider the scenario where a set of parties need to cooperate with one another. To safely exchange the information, a set of authorization rules is given to the parties. In some cases, a trusted third party is required to perform the expected operations. Since interactions with the third party can be expensive and there maybe risk of data exposure/misuse, it is important to minimize their use. We formulate the minimization problem and show the problem is in NP-hard. We then propose a greedy algorithm to find close to optimal solutions.