E-commerce of digital items and the problem of item validation: introducing the concept of reversible degradation

Abstract

Fair exchange protocols have been widely studied since their proposal, but are still not implemented on most e-commerce transactions available. For several types of digital items (e-goods), the current e-commerce business model fails to provide fairness to customers. The item validation problem is a critical step in fair exchange, and is yet to receive the proper attention from researchers. We believe these issues should be addressed in a comprehensive and integrated fashion before fair exchange protocols can be effectively deployed in the marketplace. In this work, we contextualize how the current model for buying and selling digital items fails, by overlooking the subtleties of the item validation problem, to provide guarantees of a successful transaction outcome to customers—thus being unfair by design. We also introduce the concept of Reversible Degradation, a method for enhancing buy–sell transactions concerning digital items that inherently includes the item validation step in the purchase protocol in order to tackle the discussed problems. In this paper we further explore the concept of reversible degradation (Piva and Dahab in Proceedings of international conference on security and cryptography (SECRYPT). SciTePress Digital Library, 2011) and propose a deliverable instantiation based on systematic error correction codes, suitable for multimedia content. We describe our technique in detail and provide methods for key generation, degradation and recovery, as well as a discussion about efficiency, security and flexibility. We also present and discuss experimental data, and exemplify how the technique can be useful for enabling item validation and dispute resolution in some application scenarios.