Last modified: 08/27/03 11:56:54 AM
S.W. Smith, J.D. Tygar.
``Security and Privacy for Partial Order Time.''
ISCA Seventh International Conference on Parallel and
Distributed Computing Systems.
Partial order time expresses issues central to many problems in
asynchronous distributed systems, but suffers from inherent security
and privacy risks. Secure partial order clocks provide a general
method to develop application protocols that transparently protect
against these risks. Our previous Signed Vector Timestamp 
protocol provided a partial order time service with some security: no
one could forge dependence on an honest process. However, that
protocol still permitted some forgery of dependence, permitted all
denial of precedence, and leaked private information. This paper
uses secure coprocessors to improve the vector protocol: our new
Sealed Vector Timestamp protocol detects both the presence and
absence of precedence even in the presence of malicious processes,
and protects against some privacy risks as well. Our new protocol
solves previously open security problems, and provides a foundation
for incorporating security and privacy into distributed application
protocols based on partial order time.