Usually the draw is done in one place and then the result is broadcasted live (or in front of witnesses). Not only does this entail many technical constraints, but it is also a weak link. If a malicious person tampers with the draw, the whole system collapses. We present here an alternative to this centralized draw to make the system robust and much more difficult to falsify.

To understand this method, a reminder is needed about the generation of random numbers in computers. These machines are deterministic, which means that for a given input the computer’s response is always the same. But in 1946 a famous researcher in computer science created what we call today a pseudo-random number generator. For this, he started with a number, the seed, taken from a fluctuating and unpredictable phenomenon. First he multiplied this three digit number by itself and then took the three middle digits of the number resulting from the multiplication, this selection will generate the second of the series. By repeating the operation it can produce long series of pseudo-random numbers. The prefix “pseudo” is used because the sequence is entirely determined by the seed. It is also important here to note that two strings even with very close values generate two very different sequences of numbers. Today, the generation of random numbers in computers uses much more complex manipulations than simple multiplication but the idea is still the same. The random number method that we are going to use exploits this mechanism.

We will provide all members of the association with a few lines of code. Then a person of the association will give one day in the future to select **the seed** which will be the value of the CAC40 at the closing of the market. Why a stock market index? The financial markets are unpredictable and very difficult to manipulate with precision. This method allows to make a decentralized draw, inexpensive and much harder to influence. Indeed, providing a few lines of code and a precise day is much more practical than organizing a big draw. Moreover the decentralized aspect increases the transparency because the draw can be checked and re-checked. You can use this link to draw with different seeds and verify these statements; with the seed 0 will be 2 and 3 that will be selected with 1 will be 1 and 3. Just click on the button with the play symbol, enter a value for the seed and you are in control of the gam