Provable Fairness Overview
This game is provably fair. What that means is that there is no way the site can cheat you by picking numbers to make you lose. You can take our word for it, but for the crypto-nerds out there, here are the gory details:
When you click ‘randomize’ in the top right we make up a secret random string (the server seed) that is used to randomize the rolls. You are shown the hash of the server seed, and are asked to supply your own random number (the client seed) to further randomize the rolls.
The sha256 hash of the server seed you are currently using is:
The client seed currently in use:
and the number of bets you have made using it:
Each time you roll, the server and client seeds are combined with the number of rolls you have made since the seeds were selected to create the roll.
Notice that you are shown the hash of the server seed before picking your client seed. This ensures that there is no way we can influence the numbers you will roll.
Instant Verification with a Single Seed
If you want to verify that we are not cheating you, click ‘randomize’ again to reveal the current server seed and generate a new pair of seeds for future rolls.
In this way you can verify your rolls whenever you like, without having to wait for a daily secret to be published, and you are safe from cheating without the need to set a different client seed for each bet you make.
For bets with ID less than 145,000,000:
To generate your dice rolls, we string together your client seed, a colon, and your bet number.
For example, if your client seed is 1234567 and you are about to make your first roll since setting the seed, we will use “1234567:1”.
We then use the hmac-sha512() function to hash that string with the server seed. That gives us a 128 character hex string.
For bets with ID 145,000,000 or higher:
- To generate your dice rolls, we string together your bet number, a colon, your client seed, a colon, and your bet number.
- For example, if your client seed is 1234567 and you are about to make your first roll since setting the seed, we will use “1:1234567:1”.
- We do the same with the server seed: put your bet number before and after it, with a colon separator.
We then use the hmac-sha512() function to hash that string with the modified server seed. That gives us a 128 character hex string:
For all bets:
Note that the “bet number” in both the above cases is the number of bets you have made since your seeds were selected, not the global server “bet ID” number.
We then take the first 5 characters of that hex string and convert them to a decimal integer (that will be in the range 0 through 1048575 (16^5-1)).
If it is less than 1 million, we divide it by 10,000 and use it as your dice roll. That is the case 96% of the time.
Otherwise we use the next five characters of the 128 character hex string, and repeat.
In the unlikely event that none of the 25 groups of five characters are lower than 1 million when convered to decimal, we use the remaining 3 hex digits, which give a number in the range 0 through 4095, which corresponds to a dice roll of 0.0000 through 0.4095.
A few players on the site collaborated to create a service which you can use to verify your rolled numbers. Copy the 3-line value from the ‘randomize’ window into the first input of that page and click ‘verify’ for a list of the numbers you rolled, calculated independently of the site.
You currently have BTC invested.
You are supplying of the site’s bankroll.
Be the Bank!
You can invest some of your balance with the site for other players to bet against. This both increases the maximum bets on the site, and you keep any profits made. You also ‘keep’ any losses.
Although we have a 1% house edge, and in the long run will earn a profit of 1% of the wagered amount, in the short to medium term we can still lose money. In times when we are lucky, we win many bets and earn a larger-than-expected profit, and in unlucky times we earn less than expected, and can even lose out. This is especially so if someone comes in and makes a large number of massive bets; we can either gain a lot or lose a lot. If you believe that the potential gains do not outweigh the potential losses, please do not invest.
Let’s break it down: Suppose the total bankroll is currently made of 90 BTC from a single investor, and you invest a further 10 BTC. You will have 10% of the new ‘current bankroll’, and the first investor’s share will drop from 100% to 90%. Each bet that a player makes is played against the current bankroll. As players win and lose, your investment grows or shrinks by 10% of the overall house profit. When you withdraw your investment you get 10% of the current bankroll. You may withdraw your investment at any time. Other players’ investments will affect the percentage of the current bankroll that your investment represents. If a 3rd investor then invests another 100 BTC, bringing the total bankroll to 200 BTC, the first investor’s percentage drop from 90% to 45%, your percentage drops from 10% to 5%, and the new investor’s percentage is 50%. Then if a player loses 20 BTC to the site, everyone’s investment grows in proportion. Your 10 BTC investment is now 5% of the new bankroll (220 BTC) ie. 11 BTC.
On each bet, each player can profit by up to 0.5% of the house’s bankroll. The maximum bet is dynamically adjusted after each bet. Work is in progress to allow investors to set their own risk level. Perhaps you want to risk up to 5% of your investment on each roll, not just 1%. At some point that may be available. Originally the site allowed players to profit by up to 1% of the house’s bankroll, but this figure was reduced in an attempt to reduce volatility in the bankroll levels.
A simple example: The site’s bankroll is 90 BTC. You invest 10 BTC, bringing the total bankroll up to 100 BTC. A player bets 1 BTC and loses. The total bankroll is now 101 BTC. You withdraw your investment, and get 10.1 BTC. The site’s bankroll is now 90.9 BTC.
Alternatively: You invest the same 10 BTC and the same player bets 1 BTC at a 2x multiplier and wins. The total bankroll is now 99 BTC. Your investment is now only worth 9.9 BTC. You can withdraw it now and take the loss, or wait for the law of large numbers to work in your favour. In the long run you can expect to profit 1% of everything bet against your investment.
The site currently charges a 10% commission on net investment profits to cover expenses such as advertising, server hosting, etc. The commission rate is subject to change. Notice will be given in this paragraph 7 clear days before any rate change takes effect.
Commission is charged when profits are divested, or at midnight (UTC) on Sunday each week, whichever happens sooner. Commission is never charged twice on the same profits. For example if you invest 100 BTC and it grows to 110 BTC by the end of the first week, you will be charged 10% of your 10 BTC profit. If your remaining 109 BTC investment then shrinks to 105 BTC over the next week, you will not be charged any commission at the end of that week. And then, if it grows to 119 BTC by the end of the 3rd week, you will only be charged 10% commission on the new 10 BTC of profit over the previous high of 109 BTC. At any point you could divest up to your original investment of 100 BTC without being charged commission since we consider that when divesting you divest the original investment first, and profits later.
Please help advertise the site. The more players we have, the faster your investment will grow. If you have a BitcoinTalk.org forum account, please consider adding the following to your signature there:
- To edit your BitcoinTalk signature, visit
- Deposits Withdrawals Investments
- Click the buttons above to see a report of your past activity on the site.
What is this place?
Just-Dice.com is a Bitcoin casino where you can play a fast paced dice game with a low 1% house edge and gamble with your BTC. Pick your chance to win and how much to bet, then select “hi or lo” to roll the dice and get an instant result, win or lose. There is also a live chat where you can interact with other players on the site. They will probably try to convince you to bet more. 🙂
Alternatively you can invest in the site’s bankroll, and share in the site’s profits (or losses), while helping us offer bigger maximum bets to the players. This is why the players in the chat are trying to convince you to bet more – they win when you lose…
What does 1% house edge mean?
Some people have been confused by this. They ask when we take the 1% off, is it after each win, or when they try to withdraw. It is neither of these. The house edge is built in to the payouts. When you play the 50% game and win, you receive 1.98 times your stake as your payout. If there was no house edge, you would receive 2 times your stake. 1.98 is 1% less than 2. That is the house edge.
What is Bitcoin and how do I get some?
Bitcoin is the first decentralised digital currency. See WeUseCoins.com for an introduction.
You can get a small amount of Bitcoin to try the site out at LandOfBitcoin.com where you can earn Bitcoin for watching YouTube videos.
If you are looking for larger amounts of Bitcoin, HowToBuyBitcoins.info lists many places you can buy them.
How do I deposit?
Before depositing, please confirm that this type of gambling is legal in your jurisdiction.
Then, and only then, click the ‘deposit’ button. It is in the top right. This is the most frequently asked question by far. I guess people just don’t expect it to be on a button. Your deposit needs one confirmation on the Bitcoin network before it will be credited to your account.
The wallet was reset on 20th January 2014. Using old deposit addresses from before then will require a manual step and will result in delays crediting your account. If you deposit to an old address accidentally, please contact us giving your userid (from the account tab), and mentioning that you know about the change of wallets.
How do I withdraw?
There is a ‘withdraw’ button next to the ‘deposit’ button. You will need to wait until your most recent deposit has enough confirmations before you are allowed to withdraw. The number required is the number of digits in the integer part of the number you get when you square the amount you are withdrawing. So a 31 BTC withdrawal needs 3 confirmations (31 * 31 = 961) and a 32 BTC withdrawal needs 4 confirmations (32 * 32 = 1024).
Please note that for security purposes there are limited coins available for automatic withdrawal. On attempt to withdraw more than is available, your request will fail but will be logged. Please follow up with an email to the address at the end of this FAQ confirming the amount and the destination address. Your withdrawal will then be processed manually. Support in these matters usually occurs within a few hours, but can take up to 24 hours during exceptional circumstances. Thank you for your patience in this matter as it is difficult to balance convenience and security.
How does the game work?
- select a chance to win
- set the bet size
- click roll hi or roll lo depending on whether you think your roll will be high or low (or hit H or L on the keyboard; the dark rectangles on the buttons indicate keyboard shortcuts)
Each time you roll the dice, you get a number between 0 and 100.
When rolling low, you need to roll less than the chance you selected. When rolling high, you need to roll (100 – chance) or over.
So with a 30% chance to win, low rolls win with less than 30, and high rolls win with 70 or more.
Alternatively, you can select the payout multiplier and the chance to win will be calculated for you.
Also, you can select the profit you want to make if you win, and the bet size will be calculated for you.
What is the house edge?
The payouts are set such that the house edge is .
What is the max profit?
The max profit indicator tells you how much the house is prepared to risk per roll, and is based on the size of the house bankroll. This amount remains unchanged whatever your chance of winning. It adjusts in real time as the house bankroll grows or shrinks..
For example, suppose the max profit is 500 BTC:
You can bet up to 500 BTC with a 2x multiplier (49.5% chance to win) to double your money.
Or you could bet up to 10 BTC with a 51x multiplier (1.94% chance to win) for a return of 510 BTC and so a profit of 500 BTC.
At the other end of the spectrum you could bet up to 49000 BTC with a 1.0102x multiplier (98% chance to win) for a return of 49500 BTC and a profit of 500 BTC.
How about ‘luck’?
The luck percentage displayed shows how many rolls you have won compared to how many you ‘should’ have won. For example, if you play 10 times with a 10% chance of winning and win two of the 10 rolls, your luck will show as 200%, since you have won twice as many as you ‘should’ have. Bet size is not taken into account when calculating luck, so it is possible to have a luck less than 100% and still show a profit if your winning bets risked more than your losing bets.
For example, suppose you are playing with a 50% chance to win (ie. a 1.98x payout). You bet 1 BTC and lose. You double up to 2 BTC and lose again. You double again and lose 4 BTC, and then double one more time to 8 BTC and win. You have played 4 times and won once. Your luck shows as 50% since you have won half as many games as you would expect to with a 50% chance of winning, but your profit is positive. You have lost 1+2+4 = 7 BTC and won 0.98*8 = 7.84 BTC for a profit of 0.84 BTC.
What do the colors mean in the bet list?
The number in the profit column is:
green if the player won, and
red if they lost.
The number in the lucky column is:
green if the player won, red if they would have won if they had made the opposite bet ( hi vs lo ), and
a golden brown color if they would have won whichever way they rolled given the chance to win they had chosen, and
grey if there was no way they could have won whichever way they rolled.
Can I use my balance here to play on SatoshiDice etc.?
In order to keep as few coins online as possible, Just-Dice uses a shared hot-wallet. Most deposits are moved off site soon after being received. Consequently when you withdraw you are often sent funds that somebody else recently deposited.
Because of this, if you use your Just-Dice account to send bets to such sites, any winnings are unlikely to be credited to your Just-Dice account.
Why are the dice rolls so slow?
The server can only handle a certain number of rolls per second. There are people running automated ‘bot’ programs that place tiny bets over and over. These were causing the whole site to slow down. In response to this, I introduced artificial delays to the roll, based on the amount being wagered. This slows down the ‘dust bots’ so that the site stays fast for real players. The delays are as follows:
- bets of 0.00000000 BTC are delayed by 3 seconds
- bets of 0.00000001 BTC to 0.00000009 BTC are delayed by 1 second
- bets of 0.00000010 BTC to 0.00000099 BTC are delayed by 0.8 seconds
- bets of 0.00000100 BTC to 0.00000999 BTC are delayed by 0.6 seconds
- bets of 0.00001000 BTC to 0.00009999 BTC are delayed by 0.4 seconds
- bets of 0.00010000 BTC to 0.00099999 BTC are delayed by 0.2 seconds
- bets of 0.00100000 BTC or more are not delayed
Can I get a refund?
All bets are final. The site operates with a very small house edge. Refunding bets would turn the site’s positive expectation into a negative one.
Deb wrote a blog post about this.
I’ve been asked to sign a message with my address. How do I do that?
In order to prove that you own an account, you will sometimes be asked to sign a message using the address from which you deposited. How you do that depends which wallet you are using:
If you are using bitcoin-qt, go to the ‘receive’ tab, select the address, click ‘sign message’, type a message in the large middle textarea, click ‘sign message’, and copy/paste the address, the message, and the signature. Here is a screenshot.
If you are using the blockchain.info wallet, log in, go to ‘receive money’, open the ‘actions’ menu to the right of the appropriate address, select ‘sign message’, type the message to sign, click ‘sign message’, then copy/paste the address, message, and signature. Here is a screenshot.
What if I can’t stop?
Like all forms of gambling, online gambling can become an addiction that can have serious negative effects on your life. If you lose more than you planned to or can safely afford and find yourself struggling to control time and/or money spent gambling, please check these sites for information that could help you:
Games of chance (like Just-Dice) have no memory between consecutive rounds, so increasing the amount you wager after a streak of losses has no effect on the odds of winning the next round.
You can also use the box found at the bottom of the “Account” tab to have a “cool-off” period during which you cannot gamble. “When rolling, delay my results …”. There is no limit to the number of seconds you can input, but it will only ‘last’ until the next server reboot, at which time you will need to input your delay again.
Also, if you are an investor on the site and want your account to be permanently blocked from betting, email the address found towards the bottom of this FAQ and ask to be added to the list of accounts that are not allowed to bet.
Are there many coins in a hot wallet on the server?
No, of course not. The vast majority are in cold storage, at an address I can prove is under my control:
$ bitcoind verifymessage 14o7zMMUJkG6De24r3JkJ6USgChq7iWF86 \
“This address is owned by Just-Dice.com and is used for offsite cold storage.”
> > true
Is this site a scam or ponzi scheme? Is it insolvant?
If the site was doing something simple like refusing to pay out winners, then everyone would have heard about it already.
The dice rolls are provably fair. This is addressed on the ‘Fair?’ tab on site.
As I see it, there are two non-obvious ways the site could be scamming people:
(a) We could be under-reporting the amount invested. As an investor, you can check this is not the case by looking at the list of investor balances which is updated each Sunday. Each investor can check that the list includes their invested amount.
(b) We could be spending invested coins. You can check this is not the case by comparing the site’s total invested amount with the content of the cold wallet.
The above two together should be enough to prove that (a) we don’t hide any investments, and (b) we are in control of all invested coins. In conclusion, the site is not running a “fractional reserve” operation and is in fact solvent. If you see any way the site could still be running in “ponzi” mode given the above, please let us know and we will attempt to provide further proof.
Show me some milestone bets?
You can’t just put a question mark on the end of a sentence to make it a question you know? But here they are.
- What other sites do you recommend?
- The ones that link to us, of course!
- How does this guy win every 5% bet?
The ‘all bets’ tab doesn’t really show all bets; there are too many bets to show them all. It shows all bets which risk, win, or lose an amount of 0.05 BTC or more. (This number is subject to change). If no bets have met that criteria for 3 seconds, then the next bet that happens will be shown, regardless of its size. So when someone is betting 0.01 BTC at 5% over and over, his losses mostly won’t show up, since he’s only risking and losing 0.01 BTC, but all his winnings WILL show up, since he’ll be winning something like 0.20 BTC. That’s why it sometimes looks like people are winning low chance bets over and over.
Note that the same reasoning also explains why you sometimes see people having very long losing streaks at high chances to win; their wins at high chance are too low to show up, but their losses are big enough to show.
How can I tip you?
People often offer to tip me for running the site. In the past I’ve mostly said “you don’t need to tip me; I make plenty from commission”, but have accepted a few offers. I’ve been making judgements about whether the person could afford to tip me or whether they felt obliged to, which isn’t fair given that in general I have nothing to go on in making such judgements. So please, there’s no obligation to tip me at all, but if you want to, my address is 1Z986aqTd3xYJv5LrausgkV74ky1vyR3M.
There’s a “dooglus” in the chat. Is he the real one?
Usually dooglus has a (1) in front of his name, and Deb has a (2). The passwords for these accounts are very long randomly generated strings that are quite impossible to memorise. So when out of the house, dooglus uses account (10282) which also has chat name ‘dooglus’. That account has no admin privileges, and very limited funds available, so it is safe to use on untrusted computers. The password on that account is long, but short enough to carry in a human head. If you see user (10282) claiming to be dooglus, it probably is. No other user should be able to change their name to ‘dooglus’, although variations on the theme are allowed.
What commands are available in the chat? Is it IRC?
The list of commands changes occasionally, but is always available by typing /help in the chat. It’s not an IRC chat, it’s just something built into the website.
How can I contact you?
If you need to contact us, please do so via email: [email protected] (if you want to encrypt your message, my GPG key is 4BE6A010492A358E).
You will receive an automatic reply with a link to track progress.
dooglus (1) and Deb (2) are often available in the chat tab on-site, but there is no guarantee that either of them will see anything you say there. If it is something important, please use the email address above.
On the forums there are two threads: one for players and one for investors.
Comment on Deb’s blog in which she posts irregularly about happenings on Just-Dice.