High-speed pseudorandom number generation with small memory

Abstract

We present constructions for a family of pseudorandom generators that are very fast in practice, yet possess provable strong crypto-graphic and statistical unpredictability properties. While such constructions were previously known, our constructions here have much smaller memory requirements, e.g., small enough for smart cards, etc. Our memory improvements are achieved by using variants of pseudorandom functions. The security requirements of this primitive are a weakening of the security requirements of a pseudorandom function. We instantiate this primitive by a keyed secure hash function. A sample construction based on DES and MD5 was found to run at about 20 megabits per second on a Pentium II.