What is digital timestamping?
Consider two questions that may be asked by a computer user as he or she views a digital document or on-line record: • Who is the author of this record – who wrote it, approved it, or consented to it? • When was this record created or last modified? In both cases, the question is about exactly this record – exactly this sequence of bits. An answer to the first question tells who and what: Who approved exactly what is in this record? An answer to the second question tells when and what: When exactly did the contents of this record first exist? Both of the above questions have good solutions. A system for answering the first question is called a digital signature scheme (see Question 2.2.2). A system for answering the second question is called a digital timestamping scheme. Such systems are described in [BHS93] and [HS91]. Any system allowing users to answer these questions must include two procedures. First, there must be a signing procedure with which (1) the author of a record can “s
