All I mean to say is that I'm often tempted to try and figure-out the seed(s) used to generate the puzzle keys, as I think you've spent quite a lot of time doing... But every time I think about it, I have to remind myself that we just don't know enough / have enough data about where to start... Which version of which language was used, and which RNG (standard or cryptographic, Mersenne Twister or something else, etc) was used, or whether the rand was seeded once, before the loop with a static seed (like I tend to do, which I think is kind-of a common C# pattern) or again on every loop with a dynamically changing seed (the way the code you posted was), not to mention the seed's exact value itself, and who knows what other factors...