Cumulative notarization for long-term preservation of digital signatures

The long-term preservation of digitally signed documents may be approached and analyzed from various perspectives, i.e. future data readability, signature validity, storage media longevity, etc. The paper focuses on technology and trust issues related to the long-term validation of a digital signature. We exploit the notarization paradigm and propose a mechanism for cumulative data notarization that results in a successive trust transition towards new entities, modern technologies, and refreshed data. A future relying party will have to trust only the information provided by the last notary, in order to verify the validity of the initial signature, thus eliminating any dependency on ceased entities, obsolete data, and weak old technologies. The proposed framework uses recursive XML elements so that a notarization token structure encapsulates an identical data structure containing a previous notarization token.