Then we define two hard problems, the Computation Dependent-CA (C-DCA) problem and the Decisional Dependent-CA (D-DCA) problem, all based on the Reversibility problem of CA.
The C-DCA problem is for some unknown a [member of] [Z.sub.p], computing [F.sub.ca] (a + 1).
The C-DCA assumption holds if for any probabilistic polynomial time adversary, the probability Succ(A) is negligible, where,