Appeal 2006-2107
Application 09/969,833
function g. Alternatively, one could say that g in such a situation is the
identity function. (Specification 1:27-2:3).
8. A one-way chain of the type described above can be computed
by starting with value vs and from that value computing vs-1 by application of
the one-way function to vs, then computing vs-2 by application of the one-
way function to vs-1, and so on. This is a general case of computation of the
above value y=f(x), since the value y is used as input to the one-way
function, in the next “link” of the chain. One important reason for using
such chains is to represent time. For example, if a one-way chain v1 . . . vs is
computed by a first party from an endpoint value vs, and the value v1 of the
chain is given to a second party, then the first party can “increment time” by
showing consecutive pre-images v2, v3, etc. to the second party. Note that
the second party cannot compute these consecutive pre-images from v1 on its
own. However, given a pre-image v2, the second party can verify the
correctness of that pre-image by checking if v1=f(v2). For v3, this
verification would have two steps, a first in which v2 is computed, and a
second in which v1 is computed and compared to the known value v1.
(Specification 2:11-22).
9. In accordance with the invention, so-called helper values are
positioned and utilized in a manner which substantially reduces the storage-
computation product associated with generating chain values. (Specification
7:9-11).
10. Helper values are also generally referred by Appellant as
“pegs.” Each peg may therefore be viewed as having a single helper value
associated therewith, the helper value being the value vi of the chain at the
peg position. (Specification 8:16-19).
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