Re: Jetty Session ID Prediction

Amit Klein wrote:
Chris Anley wrote:
Hi folks,
I've posted a paper that explains a little more here:

Nice paper. I do notice an enumeration loop over 2^16 possible 16-bit
values. This can be improved as following (note: this is probably
already discussed in mathematic literature - i.e. I probably did not
invent it...):

<lots of cool stuff cut>

This should be much faster than looping over 2^16 values.

Cheers Amit, that's cool and I'm sure it's faster. There are quite a few
neat tricks in the literature - Knuth's paper on predicting lcg's where
you're missing the low bits is good (I was trying to work out whether
his technique and yours are equivalent; I'm still not sure...), and the
paper Michal Zalewski recommended:
is also neat. One interesting (?) question is whether that technique
applies to the mysql rand, which is wierd and custom, and used in the
auth protocol prior to version 4.1.

I don't think anyone's published the code for a totally generic
predictor before, but I might be mistaken. If anyone knows, could they

Anyhow, ultimately, it's a POC for a specific bug.
I loop over 2^16 values because it's instant, and easy. :o)




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