A framework to evaluate security and cost of time stamping schemes
Time stamping is a technique used to prove the existence of certain digital data prior to a specific point in time. With the recent expansion of electronic commerce, it has been widely recognized as all important technique for ensuring the integrity of digital data for a long time period. Recently, various time stamping schemes have been proposed. However, a framework for evaluating their security and cost has not yet been established. Therefore, it has been difficult for users and system designers to select appropriate time stamping schemes. This paper presents a new framework for evaluating the security and cost of time stamping schemes. Our framework classifies time stamping schemes into 108 categories and clarifies their characteristics with regard to security and cost. By applying our framework to a certain scheme, we can easily evaluate its security and cost without discussing details of its specification. In this paper, we explain the basic idea of our framework and show how to use it by applying it to four existing schemes: Digital Notary/SecureSeal, PKITS, TIMESEC and Cuculus.
time stamp security evaluation cost evaluation