## One-Way Functions and Balanced NP

1992-05-01
Lutz, Jack
##### Organizational Units
Organizational Unit
Computer Science

Computer Science—the theory, representation, processing, communication and use of information—is fundamentally transforming every aspect of human endeavor. The Department of Computer Science at Iowa State University advances computational and information sciences through; 1. educational and research programs within and beyond the university; 2. active engagement to help define national and international research, and 3. educational agendas, and sustained commitment to graduating leaders for academia, industry and government.

History
The Computer Science Department was officially established in 1969, with Robert Stewart serving as the founding Department Chair. Faculty were composed of joint appointments with Mathematics, Statistics, and Electrical Engineering. In 1969, the building which now houses the Computer Science department, then simply called the Computer Science building, was completed. Later it was named Atanasoff Hall. Throughout the 1980s to present, the department expanded and developed its teaching and research agendas to cover many areas of computing.

Dates of Existence
1969-present

Related Units

##### Abstract

The existence of cryptographically secure one-way functions is related to the measure of a subclass of NP. This subclass, called BNP (``balanced NP''), contains 3SAT and other standard NP problems. The hypothesis that BNP is not a subset of P is equivalent to the P <> NP conjecture. A stronger hypothesis, that BNP is not a measure 0 subset of E_2 = DTIME(2^polynomial) is shown to have the following two consequences. 1. For every k, there is a polynomial time computable, honest function f that is (2^{n^k})/n^k-one-way with exponential security. (That is, no 2^{n^k}-time-bounded algorithm with n^k bits of nonuniform advice inverts f on more than an exponentially small set of inputs.) 2. If DTIME(2^n) ``separates all BPP pairs,'' then there is a (polynomial time computable) pseudorandom generator that passes all probabilistic polynomial-time statistical tests. (This result is a partial converse of Yao, Boppana, and Hirschfeld's theorem, that the existence of pseudorandom generators passing all polynomial-size circuit statistical tests implies that BPP\subset DTIME(2^{n^epsilon}) for all epsilon>0.) Such consequences are not known to follow from the weaker hypothesis that P <> NP.