In this paper, we study the security of the Micali-Schnorr pseudorandom number generator. The security of this cryptographic scheme is based on two computational problems which are variants of the RSA problem. The RSA problem essentially aims at recovering the plaintext from a random ciphertext. In the analysis of the Micali-Schnorr pseudorandom generator, we are interested in instances of this problem where the plaintext is small and where the ciphertext is not entirely known. We will describe time / memory tradeoff techniques to solve these hard problems which provides the first analysis of this pseudoran-dom generator 25 years after its publication.