Trusted and Transparent Time-Stamping Through TEEs and Network Time Security

Abstract

Digital timestamps are essential for proving the existence of a digital document at a certain point in time. Time Stamp Authorities (TSAs) provide users with a mechanism for obtaining digital cryptographic signatures binding documents to points in time, which can be verified at a later time. However, this process requires that both the party obtaining the signature and the party verifying the signature trust the TSA's faithfulness, its time source, as well as its security practices. Conversely, operators of TSAs must themselves take extreme caution to meet these expectations. We devise a novel TSA-like architecture based on TEEs and show that this architecture, when coupled with access to a transparent set of secure time sources, can provide the user, the verifier, and the operator of the TSA with a high level of assurance.