Digital confidentiality agreement as a smart contract
The objective is to build a smart contract which can allow Alice and Bob to share confidential information in a way which encourages by game theoretic incentive confidentiality between Alice and Bob.
1) An arbitrator
To accomplish this you need a third party to the smart contract called an arbitrator. The arbitrator is basically functioning like a judge. This arbitrator could be an agency, it could be an individual, or a DAC but it will have to determine if both sides abide by the confidentiality agreement.
Each side in the confidentiality agreement must accept an equal amount of risk in order to be given a stake in the success of keeping confidentiality. To buy this stake Alice would have to give a specific amount of value to the smart contract as collateral. This amount of value indicates how much Alice can be trusted as measured by the amount of risk she is willing to take, and as a result Bob would have to take on an equal amount of risk by giving an equal amount to the smart contract as mutual collateral.
To enforce the smart contract the information shared simply has to remain confidential. If there is a leak which takes place then to enforce the contract the collateral for both Alice and Bob are destroyed in an act of mutually assured destruction. The contract is enforced by psychology and game theory where Alice and Bob can trust one another because they each are taking on an equal amount of risk. The threat of mutually assured collateral destruction by the arbitrator is what enforces the digital confidentiality agreement smart contract.
This would allow an arbitrator to be rated so that only arbitrators with a good reputation for successful arbitration could be paid. Reputation for settling disputes could be tracked, every dispute should be recorded in a public record so that over time arbitrators can gain a track record from their history. This track record should allow arbitrators to charge higher fees over time until the market place is filled with skillful arbitrartors with good reputations.
This smart contract would be relatively easy to write. It would require only a trusted arbitrator, an escrow account to hold the mutual collateral, and an enforcement mechanism which involves shared destruction of collateral. The shared destruction could happen all at once or it could slowly drain as this could all be negotiable. The arbitrator would be the person who has the power to trigger the shared destruction and because the arbitrator would have a reputation to maintain they would not be able to recklessly use the nuclear option.
In the case where there is a leak from either Alice or Bob then either of them could alert the arbitrator which would allow the arbitrator to study the facts to determine if there was a leak. If there was a leak then the arbitrator could have the power to destroy the collateral so that the pain is spread. It would not be a situation where Alice or Bob would want to approach the arbitrator unless the leak is something significant.
The arbitrator could also be given the power to determine that one side leaked on the other and destroy the collateral for the side which leaked. This would be quite difficult to prove though. This smart contract design may not be perfect so please improve upon it.