Hi, I've been wondering about the proper application of statistics with regard to comparing PRNGs and encrypted text to truly random sources.
As I understand it, when looking at output, one can take a hypothetical source model (e.g. "P(0) = 0.3, P(1) = 0.7, all bits independent") and come up with a probability that the source may have generated that output. One cannot, however, say what probability such a source had generated the output, because there is an infinite number of sources (e.g. "P(0) = 0.29999.., P(1) = 7.000..."). Can one say that, if the source must be A or B, what probability it actually was A (and if so, how)? Also, it strikes me that it may not be possible to prove something cannot be distinguished from random, but that proofs must be of the opposite form, i.e. that some source is distinguishable from random. Am I correct? Are there any other subtleties in the application of statistics to crypto that anyone wishes to describe? I have yet to find a good book on statistics in these kinds of situations, or for that matter in any. As an aside, it's amusing to see the abuse of statistics and probability in the media. For example, when people ask "what's the probability of <some non-repeating event or condition>?" -- "Curiousity killed the cat, but for a while I was a suspect" -- Steven Wright Security Guru for Hire http://www.lightconsulting.com/~travis/ -><- GPG fingerprint: 9D3F 395A DAC5 5CCC 9066 151D 0A6B 4098 0C55 1484 --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]