Use the middle square method: https://en.wikipedia.org/wiki/Middle-square_method https://en.wikipedia.org/wiki/Middle-square_method It can be trivially calcul

Use the middle square method: https://en.wikipedia.org/wiki/Middle-square_method https://en.wikipedia.org/wiki/Middle-square_method It can be trivially calculated with pencil and a paper and will be random enough. You just need to pick a seed and off you go. If it was good enough for Von Neumann it is good enough for you.