SIAM J. COMPUT. Vol. 22, no 6,pp. 1163-1175, December 1993 ON THE EXISTENCE OF PSEUDORANDOM GENERATORS ODED GOLDREICH , HUGO KRAWCZYK , AND MICHAEL LUBY Abstract. Pseudorandom generators ( suggested and developed by blum and micali and yao ) are efficient deterministic programs that expand a randomly selected k-bit seed into a much longer pseudorandom bit sequence that is indistinguishable in polynomial time from an (equally long ) sequence of unbiased coin tosses. A fundamental question is to find simple conditions, as the existence of one-way functions, which suffice for constructing pseudorandom generators. This paper consider regular functions, in which every image of a k-bit string has the same number of preimages of length k. This paper shows how to construct pseudorandom generators from any regular one-way function. Key words. Pseudorandom generators, one-way functions, cryptography, randomness, complexity theory.