OK, I have been doing a few numerical experiments on hash functions to see if all this stuff I have been saying is true. I took the folowing function, as my n bit to n bit hash function. first n bits(md5(n bits)) and iterated it to see how many colisions there were. I found that the total entropy in the result typically decresed by 50% for n=8,10,12,14 and droped like a rock when you itterated these. I have a couple of questions, 1) is this a good hash function, or am I missing something here. 2) the expected collision rate for rand functions is much lower. I am at a loss to explain md5. I will be trying smaller versions of all of the suggestions here to see if they help or hurt, and will set them up to run on the spare cycles on a machene or two around here. Any comments on my stratigy are appreciated in advance of me running the calculatios. Roger.