On the subject of verifiable fair betting. in the early 1900's the mob "numbers game" which in my understanding is a sort of lottery, used low order digits from the closing price of well known stocks to pick their numbers.

People could trust the the numbers were fair because they were generated and published outside the domain of the person running the game, it would be very hard to fix the cent values generated by stock activity and the same numbers were published in all the newspapers.