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The key is the weakness

Posted By: Timothy Chow
Date: Friday, 12 May 2017, at 9:29 p.m.

In Response To: The key is the weakness (Tom Keith)

Tom Keith wrote:

(I'm assuming you have to use a brute-force method to figure out the initial seed -- i.e., go through all 100,000,000,000,000 possible seeds to see which one matches the first 10 rolls.)

You can do much better than brute force with the Mersenne Twister. For a computer, it's a trivial task to solve for the seed using linear algebra.

I'm not sure about Timothy's method of back-solving to find a 6-digit internal seed that generates the desired sequence of rolls. Once you've reached the 10th or 11th roll there would be only one seed that matches the generated dice.

Recall what I said:

Note also that if we try to compensate for this problem by having the app secretly generate more digits of the seed, then a new problem arises:

The Mersenne Twister can accommodate a very large seed. If you use all the digits of the seed then you should be able to match a sequence of several thousand rolls.

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