Some Critical Aspects of the PKIX TSP

Authentication, non-repudiation, and digital signatures, require the ability to determine if a data token existed at a certain moment in time when the creator's credentials were valid. Time-stamps are tokens which contain a verifiable cryptographic link between a time value and a data representation. The paper presents some critical aspects of the X.509 Public Key Infrastructure Time Stamp Protocol, trying to suggest some possible improvements to the protocol.