Inverse function of Java's Random function

Question

Java\'s Random function takes a seed and produces the a sequence of \'psuedo-random\' numbers. (It is implemented based on some algorithm discussed in Donald Knuth, Th

Answer 1

I normally wouldn't just link articles... But I found a site where someone looks into this in some depth and thought it was worth posting. http://jazzy.id.au/default/2010/09/20/cracking_random_number_generators_part_1.html

It seems that you can calculate a seed this way:

seed = (seed * multiplier + addend) mod (2 ^ precision)

where multiplier is 25214903917, addend is 11, and precision is 48 (bits). You can't calculate what the seed was with only 1 number, but you can with 2.

EDIT: As nhahtdh said there's a part 2 where he delves into more of the math behind the seeds.