Integrating XML Linked Time-Stamps in OASIS Digital Signature Services

The technique of electronic time-stamping allows a client to get an electronic proof of the existence of a document at a specific point in time. A simple way to achieve this is to produce a digital signature over the pair (document,time). Linked time-stamps have an advantage over these simple time-stamps because they construct a verifiable link between time-stamps. In this paper, we discuss how to include linked timestamps in the OASIS Digital Signature Services standard. We highlight the problem points when introducing a sub-profile of this standard, and we describe some additional structures that are needed to accommodate a broad range of linked time-stamping schemes.