SIMPLE CONSTRUCTIONS OF ALMOST K-WISE INDEPENDENT RANDOM-VARIABLES

We present three alternative simple constructions of small probability spaces on n bits for which any k bits are almost independent. The number of bits used to specify a point in the sample space is (2 + o(1))(log log n + k/2 + log k + log 1/epsilon), where epsilon is the statistical difference between the distribution induced on any k bit locations and the uniform distribution. This is asymptotically comparable to the construction recently presented by Naor and Naor (our size bound is better as long as epsilon < 1/(k log n)). An additional advantage of our constructions is their simplicity.