New Time-Stamping Scheme Using Mutual Communications with Pseudonymous Clients

Akira YAMADA  Shinsaku KIYOMOTO  Toshiaki TANAKA  Koji NAKAO 

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences  Vol.E87-A  No.1  pp.182-189
Publication Date: 2004/01/01
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Cryptography and Information Security)
Category: Applications
Keyword: 
time-stamp,  linking scheme,  forward or backward dating attack,  pseudonymous,  mutual communication, 

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Summary: 
Linking schemes have been proposed assuming the model where the time-stamp issuer need not be trusted. However, in that environment, a fake chain attack and forward or backward dating attacks are still a residual risk in Time-Stamping services (TSS). In this paper, we propose a new time-stamping scheme that focuses on these problems. In our scheme, we use pseudonyms to prevent the time-stamp issuer from dating the time that the specific entity requests. Our scheme doesn't rely on only one trustworthy entity, and uses mutual communication between each entity. Two types of entities, server and clients without any trustworthy entities are configured in our system. The server provides an anonymous communication channel, but doesn't provide TSS, and the clients are not only time-stamp requesters but also issuers. So, when a client requests a time-stamp from the system, it is issued by one of the other clients.