Abstract: A time stamping protocol has two stages referred to as the ticketing stage and the certification stage. During the ticketing stage, the document or other identifying data is sent to the TSA. The TSA generates a “ticket” based on the document or other identifying data and a time indication derived from a trusted clock. The ticket, which serves as an unsigned time stamp receipt, is transmitted back to the document originator. During the certification stage, the holder of the ticket requests a certified time stamp receipt by presenting the ticket to the TSA. The TSA verifies the ticket and generates a signed time stamp receipt, called the ticket stub, which is then transmitted back to the document originator.

Abstract: A system and method for unique authentication of each replication of a plurality of soft-copy documents, forming a group. One soft-copy document, out of the group, becomes a carrier for an authentication code aimed at protecting the group. The authentication code is computed from the concatenation of the plurality of soft-copy documents and a key. A random number is also generated for each replication of the group of files. The random number is combined with the authentication code to mark the soft-copy document which has been selected to become the carrier. Thus, the invention introduces randomization in the insertion of the authentication code so that for each replication of an identical group of data files, unique authentication data can be associated, merged and hidden in the transmitted information.