Bitcoin Dice

By: David Marc
Updated: December 1, 2017


Over the past 3-4 years, Bitcoin Dice has become the embodiment of bitcoin’s potential to transform the online gambling experience. Simple, provably honest and instant, these games have delighted bitcoin holders and, as late as November 2014, have accounted for approximately 50% of bitcoin transactions.

In Bitcoin Dice, player’s wager whether a “dice roll” will be over or under a predetermined number. Generally, the player himself is able to determine the number under or over which he must throw to win the bet, and the payout changes according to the odds. For instance, imagining that the dice roll is on a scale of 1-100; a 50-50 bet would require the player rolling higher than a 50. However, if the player wanted a greater return at higher risk, they could choose to change the roll to over 75 for instance, a 25% chance.

The house edge is generally between 1-2%, and this is calculated in the payout. In the above examples and assuming a 2% house edge, a successful 50-50 roll on a 1 mbit bet (100th of a bitcoin) would return the player an additional .98 mbits on top of his bet. An over 75 wager would return 3.92 times the bet.

While simple, the ability of players to change the odds at will adds an extremely engaging dynamic. However, how can a user ensure that the resulting roll is fairly achieved, that the dice are not digitally loaded?

Bitcoin dice is the most popular provably fair game, accounting for the vast majority of overall gambling transactions. Dice games are offered both on and off-chain. We describe the betting and fairness mechanism below.

off-chain bitcoin dice

We discuss in our provably fair article how exactly cryptographic hash functions are utilized to ensure fairness, and we assume here basic understanding by our readers. As it pertains to off-chain bitcoin dice, three inputs are used to determine the dice roll – a predetermined server seed, which is shown in hashed format to the player; a client seed input by the player; and a nonce which correlates to the number of the particular dice roll within the current gaming session (the first roll generating a nonce of one, the second roll generating a nonce of two, and so on). After each session has been completed, the “raw” or unhashed server seed is shown to the user, who can check that, when combined with the inputs, the outputs of the session match.

The output is called a hex string, and is comprised of seemingly random letters and numbers. The dice operator will generally take the first five digits of the string, convert any letters into numbers in some standard and pre-explained fashion, thus arriving at a number somewhere between 1-1000000. This number is then divided, achieving a roll between 1-100. The important thing to stress is that the process for arriving at a number from the hex string is universally known and easily determined to have been done properly.

Best of the off-chain dice operators

PrimeDice is the most well-known off-chain dice operator. They exploded onto the scene in May 2013 when, on launch, a whale immediately won over two hundred bitcoins, which were promptly paid out. While a difficult hit for any new operation to weather, their honesty and transparency – the event played out in real time on the forums – was appreciated by the community and resulted in a priceless PR event.

They claim to have since processed over 4 billion dice rolls, which are streamed in real time for users to check. Probabilities can be determined by the player, by either choosing the number over/under which to roll, or picking the desired payout. Players need not register for one-time sessions – any winnings are automatically transferred to a user, minus a transaction fee of .0005 bitcoin. However, to monitor playing logs and performance, as well as to earn achievements – which results in a greater number of bitcoin that can be claimed from the primedice faucet – it behooves the player to enter a username and email. Speaking of the faucet, Prime Dice periodically offers a happy hour allowing players to claim 10,000 satoshis, and can cash if 50,000 is reached. 10,000 can be claimed every minute, so for users who have busted out, this is an excellent way of getting back into the game.

PrimeDice recently exited the United States and Australia to reduce any legal exposure. For US and Aussie players, Just-Dice is the most established brand, while is a new interesting product as well. Both games are basically the same as PrimeDice, though Just-Dice offers an interesting invest feature allowing users to essentially act as the house.

On-chain Bitcoin Dice

The now-legendary Satoshi Dice was developed by a coder known as fireduck who, concerned by regulatory issues, sold his product to Erik Voorhees in April 2012. Mr. Voorhees sold shares of Satoshi Dice at .00328 bitcoin per share ($0.032 at time of sale) on Romania’s bitcoin securities exchange, MPEx. A little over a year later in June 2013 the company was sold for 126,315 bitcoin, or $11.47 million. Investors were paid out .0035 bitcoins, or $0.32 a share, representing a profit of close to 10 times – 99% of which was due to the natural increase in the price of bitcoin. A number of imitators have since arisen, but Satoshi Dice is the first of its kind.

Satoshi Dice displays a number of bitcoin addresses, each assigned a publicly displayed number between 1 and 65,535. A player sends bitcoin to a chosen address, and if the “roll” is lower than the number assigned to the address, the player wins. The odds change with each address depending on how low the number is, so the player is not only able to determine the size of the wager, but the chances for winning. Odds range from .0015% to 97.6563%, with payouts from 1.004 to 64,000 times the wager.

Satoshi Dice has not accepted US traffic for the last year. For alternatives, check out bitzillion’s unoriginally named Satoshi’s Bones. Both Satoshi Dice and Satoshi Bones offer up a house edge of 1.9x.

Learn more about dice and bitcoin gambling in general.