Trusted Archiving

Digital signatures are a powerful tool for demonstrating data integrity and performing source authentication. Timestamps are a powerful tool for confirming data existence by a particular point in time. Today, the value of digital signatures (and timestamps containing digital signatures) is limited due to a lack of tools and techniques that address the problems associated with digital signatures that accrue over time, including: expiration, revocation, cryptanalytic advances and computational advances. In this paper, we describe a system concept and protocol to achieve secure storage of data for long periods with preservation of integrity. The approach uses periodically refreshed time stamps to address these problems. The techniques can be used for a wide variety of applications, including those requiring long-term non-repudiation of digital signatures. The concept and protocol are based on minimizing trust in individual system components in order to reduce the security requirements for those components and to enhance the trust in the overall system. A proof-of-concept implementation based on the ideas and protocol described in this paper has been developed and successfully tested. 1