Appeal No.2003-0446
Application No.09/127767
challenge-response authentication protocols, and therefore would
have been familiar with choosing one of the three above options"
(Answer, page 3) where by options he means one of random number,
count value (otherwise known as sequence) and timestamp. In his
Brief (page 15), the Appellant challenges the assertion that
Menezes discloses such interchangeability and further submits
that there is no requisite teaching or motivation presented for
such a modification, since Examiner merely concluded that one
could do so and not why one would do so. Thus, the focus is on
the inadequacy of motivation presented as to why one would
interchange the random number with a count value.
A careful look at Menezes discloses the following: time-
variant parameters such as random numbers, sequences (i.e., count
value) and timestamps are used in identification protocols to
counteract replay and interleaving attacks. These protocols are
in fact schemes put into place to reduce the vulnerability of the
system so that when the communication line between two parties is
monitored the response from one would not provide an adversary
with useful information for subsequent identification (Menezes,
page 397, paragraph 10.3.1). The time-variant parameters provide
different securities, have strengths and weaknesses (random
numbers are better at providing timeliness whereas count values
are better at providing uniqueness), can be used in conjunction
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