Analysis of an incentives-based secrets protection system

Once electronic content has been released it is very difficult to prevent copies of the content from being widely distributed. Such distribution can cause economic harm to the content's copyright owner and others. Our protocol, SPIES, allows one party to sell a secret to second party and provides an economic incentive for two parties to limit sharing of a secret between themselves. We do not use watermarking or traditional DRM mechanisms. We focus on content which is to be shared between two parties only, which is valuable, and which only needs to be protected for a limited amount of time. Examples include passwords to a subscription service, pre-release of media for review, or content shared but bound by a non disclosure agreement. With SPIES, any possesor of the content can receive a portion of the funds placed in escrow by the two legitimate possesors. We analyze this system and show that the best strategy of the content provider and content consumer to maximize their utility is to use SPIES and not share the content further. We deal successfully with a "dummy registration" attack in which multiple false identities are used in an attempt to get a higher payment. We also discuss how to determine the correct escrow amount.