By IFP I assume you mean the Integer Factorization Problem. But exactly what do you mean by that?
Are you asking if it's in P (solvable in polynomial time) or not?
If it is do you want to know how to solve it?
If it's not in P do you want a proof it's in NP (takes an exponential function of the length of the number)? Or could it be of intermediate difficulty?
AFAIK it's not NPcomplete because it can be solved in probably polynomial time by a quantum computer running Shor's algorithm. So if IFP is NPcomplete a quantum computer can solve any NPcomplete problem which is unlikely.
Chris
