# Practical (and secure) PRGs

Does anyone know if there exists a PRG construction which takes as input an (RSA-sized) integer seed and outputs a fixed number of bits? There are number-theoretic PRGs such as the RSA, Micali-Schnorr, and BBB algorithms (see http://cacr.uwaterloo.ca/hac/about/chap5.pdf), but these require one to know both the seed and other parameters used in the construction (e.g., the modulus $n$). I need a construction that only requires the random integer seed as input. I'm aware that I could potentially fix a universal set of public parameters and then just specify the integer seed, but I'd like to avoid that since the parameters would likely need to be refreshed after a certain number of invocations or uses.

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Why do you want to use a number-theoretic PRNG in the first place? There are many nice stream ciphers which are faster and stronger. –  CodesInChaos Feb 5 at 10:35