German tank problem

Re:German tank problem by Robin_Message on Friday February 21, 2014 @02:10PM (#7278755)

So, I HMAC the serial numbers of the tank. Now you have a series of very large numbers, evenly distributed.

Someone else can do the proof, but I'm pretty sure the total number of tanks is inversely proportional to the smallest difference between two observed HMACs (or between the highest observed HMAC and the highest possible HMAC).

EDIT: Actually, scratch that. That only works if you see all the tanks...

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Re:German tank problem by herge on Friday February 21, 2014 @03:23PM (#7279171)

If the serial numbers are randomly distributed in some finite span, and you have the serial number of three tanks, say:

    a: 000001
    b: 000101
    c: 100000

What is the probability that c is not the highest serial number and that there are 1000 total tanks.

How many tank serial numbers would we need before those probabilities get > 90%, > 95%?

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