Improving secure long-term archival of digitally signed documents

Long-term archival of signed documents presents specific challenges that do not need to be considered in short-term storage systems. In this paper we present a Secure Long-Term Archival System (SLTAS) that protects, in a verifiable way, the validity of today's digital signatures in a distant future. Moreover, our protocol is the first proposal that provides a proof of when a signature was created, without the possibility of backdating. We include a description of our scheme and an evaluation of its performance in terms of computing time and storage space. Finally, we discuss how to extend our system to achieve additional security properties. This paper does not focus on the long-term availability of archived information. nor on format migration problems.