Quote from: Mike Mayor on May 07, 2017, 04:05:49 PM

I feel I should quote this to refresh it for others because that is the best explanation I have ever read I am even bookmarking it. I have a wuestions though. Let us for the sake of argument assume we are dealing with a serious scammer/thief. Now the question I have is if the hash is given what happens between that had and the out put ? It could be changed to output a loss even if it was a win. Ok I k ow what you will say. You will say that is what the hash history is for. But what if that is faked somehow ? How many people actually check ? I am not sure if you can do this that is why I ask.

Hey, glad to know that you liked my tutorial

Now about your question, if the string is given before your wager, and then after your wager you check it as I explained in the tutorial, and the outputs are exactly the same, then you can be totally sure it's provably fair.

What you are proposing is VERY HARD (practically impossible) to achieve.

It's very unlikely to have a collision using MD5 Hash (two inputs with the same output), it's not impossible, but in this case it would be incredibly hard (pretty much impossible) to manipulate every single bet by changing the input to get the same output but with a different result for your bet.

Let's take the numbers from my example:

Input: R3U0nB8GcZKadHbeDq2f-0

Output: 0ae0190fe1f6830c5b480dcd26c2fbb4

Now let's take exactly the same input but changing the result:

Input: R3U0nB8GcZKadHbeDq2f-1

Output: 2d5e4d48786441a4fdbf929790da9445

As you can see, the outputs are totally different, hence the result can't be changed so easily to manipulate the bet. In this case, we would have to find an input with approximately the same length and ending in "1" that gives us exactly the same MD5 Hash result, for every single bet, which is practically impossible.

I hope I was clear enough, let me know if you have any other doubt!