Establishing authenticity is of particular relevance to digital environments, due to the ease with which data can be altered. When retaining digital resources for the long term, preservation of the media and of the software technologies will serve only part of the need [Gra94]. A future user must be assured that a particular digital object has not been subject to unauthorised changes, either accidental or deliberate. Therefore, it is crucial to care for a document's Intellectual preservation, which addresses the integrity and authenticity of the information as originally recorded.
Basically, two inherently different ways can be distinguished, by which a document can be corrupted form its original form: (1) it has been subject to distortions caused by archival processes or, particularly, the preservation strategy, or (2) it was altered by an unexpected action, due to an unknown side-effect to a routine, or by a malicious manipulation committed by a third person.
The former should be avoided at best. In case this is not possible or entails insupportable additional expenses, a detailed history of actions performed and the resulting changes to the digital object must be recorded. This documentation will allow the reconstruction of the collection item as it originally was.
In order to guarantee that information is not corrupted without knowing it or maliciously altered, a document must be authenticated. The technique used should be easy to apply and durable over long periods of time. Therefore, an algorithmic solution is favoured. Emerging technology such as digital signaturing [Blo01], digital watermarking [Kat01], or digital time-stamping [MGB01] tackle this challenge. Even though these methods make use of cryptographic theory, the encryption of documents is not required, which retains them accessible. They are means of authenticating not only a particular document, but they record authorship, protect against unauthorised copying, or prove the existence of the very document at a specific time, respectively.
Another important role might play the implementation of unique and persistent digital identifiers. These legacy identifiers require the assignment of a new identifier each time a document is modified. Current initiatives include the Uniform Resource Name (URN)9 and the Digital Object Identifier (DOI)10.