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Author Topic: Provably fair blackjack  (Read 292 times)
WhiteRiverTeam
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December 06, 2017, 03:10:31 AM
Last edit: December 07, 2017, 06:44:15 AM by WhiteRiverTeam
 #1

Hi
who can write script or sell (or become a partner) provably fair a blackjack game?
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Spendulus
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December 06, 2017, 03:54:42 AM
 #2

Hi
who can write or sell (or become a partner) provably fair a blackjack game?

Cannot exist, some people count the deck. Some dealers count the deck.

"Fairest" is 4 deck shuffle.
skycream
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December 07, 2017, 05:51:31 AM
 #3

I can't understand what you say.

 How about bitdice? They insist it is provably fair!
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December 07, 2017, 10:55:45 PM
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I can't understand what you say.

 How about bitdice? They insist it is provably fair!

For a digital game to be provably fair it means you have data about the next thing you do BEFORE actually doing it so you can prove (AFTER playing) that what you did was decided before you actually made a bet and started the round. For better understanding let's make an example by supposing you play a simple dice game where you can roll a number between 1 and 10 (so you have 10 possible values you can get in total, which are 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10). It is considered to be provably fair if the site tells you in advance what the next roll will be (not necessarily in an understandable or decriptable format at the beginning). After you play then you can verify that the result corresponds to what the site said. For example they can give you the hashed value of the next roll but you won't be able to know what the next roll will be untill you make a bet and play (you can go from "roll" to "hash" but not from "hash" to "roll").

Hi
who can write script or sell (or become a partner) provably fair a blackjack game?

Hi
who can write or sell (or become a partner) provably fair a blackjack game?

Cannot exist, some people count the deck. Some dealers count the deck.

"Fairest" is 4 deck shuffle.

You can try and implement a script that makes your game provably fair, tho' I don't really know if that's possible at all for two main reasons:
1. I don't even know what the rules of black jack are;
2. Being a cards game I don't know if you can really write such a script since every time one card goes out it cannot go out again so your data will change every single time.
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December 08, 2017, 02:49:43 AM
 #5

I can't understand what you say.

 How about bitdice? They insist it is provably fair!

Yes you can understand. I ignore bit dice, doesn't matter what they say to take your money.
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December 08, 2017, 02:51:02 AM
 #6

There are plenty of examples of "Provably Fair" blackjack... crypto-games.net has BJ on their site... the basic process works like this:

The "Rules" they implement are:
Rules:
- 4 decks
- Shuffle after each hand
- Dealer hits on Soft 17
- Double on any two cards
- Hit split aces
- Surrender
- Blackjack pays 6:5
- Blackjack is paid on split hands

To "create" four decks of cards... they simply assign a "value" to each card from the numbers 0-207 (Four decks = 4*52 card = 208 cards)...

As they explain in their "Provably Fair" section for BlackJack:
Last server seed SHA256: Last seed generated on our side (encrypted SHA256)
Last server seed: Last server seed generated by our side
Last client seed:Last client seed generated on your side
Next server seed SHA256: Next server seed (encrypted SHA256)
Next client seed: Your next client seed
SHA512 hash: Server seed and client seed combined and encrypted in SHA512

To check if your last bet was truly fair, go to an online SHA512 generator, copy Server and Client seed and for a result you'll receive SHA512 hash.

Then, convert characters from Hexadecimal to Decimal in sets by two. If decimal result finish with digit between 0-207, then this digit represents one card. Each card has its own number. List of cards and their assigned numbers can be found here. If the number is picked twice, or if it's higher than 207, then the step is skipped.

Basically, they generate a SHA512 from the Server and Client seeds (The "encrypted" SHA256 hash of the server seed and your client seed can be viewed PRIOR to the hand being dealt) and start converting the bytes from that SHA512 to numbers between 0-255... these are matched to the 0-207 values assigned to the cards and as stated, if the number is picked twice (ie. card already used) or higher than 207 (card doesn't exist), it is ignored and next number from 0-255 is used...

Each card is then displayed in turn as you play the hand... AFTER the hand, you will be shown the unencrypted server seed... which you can then SHA256 and prove that it matches the SHA256 hash that you were shown BEFORE the hand to prove that the site hasn't changed anything... = Provably Fair = they cannot change the results.

A lot of people fail to grasp how all this works and regularly accuse the various betting sites of "cheating" when they hit a bad losing streak Roll Eyes




Worked Example:

The "secret" server seed for the next hand is: ServerSeed1 (you CANNOT see this prior to the hand starting)
The SHA256 code they would display would be: b41c9d6dc789242d3a4515c150b3141aaae41547f61ca2767881cb79fc46e981 (you CAN see this prior to the hand starting)

You client seed is set to be: ClientSeed1

As per CG.net's process, the server takes  "server seed + client seed" = "ServerSeed1ClientSeed1" giving a SHA512 of:
3205644f639e62da116a6fbb2a93ea0c689e546b4217fc6ef90423ba2af7c30b4b23ec544b53166 ac11618621780b1bdc0de8dbe1caf9a806d4184a33293eff2

You split it up into hex groups of 2 chars so that you end up with "card values" of: 32, 05, 64, 4f, 63, 9e, 62, da, 11, 6a etc etc...
Which converted from hex to decimal = 50, 5, 100, 79, 99, 158, 98, 218...

Converting from the published list of cards = QC, 6S, 10C, 2D, 9C, 3S, 8C, "Out of Range ignored"... etc

Which would most likely result in the following BJ result:

Player: QC
Dealer: 6S
Player: QC+10C (stands on 20)
Dealer: 6S+2D+9C (stands on 17)

Player wins! Smiley

After the round is finished, the server will publish the previous rounds "server seed"... which was ServerSeed1... you can then do all the checking... first check that the SHA256 of ServerSeed1 = b41c9d6dc789242d3a4515c150b3141aaae41547f61ca2767881cb79fc46e981 -CHECK OK!

Then check that ServerSeed1ClientSeed1 = SHA512 used... 3205644f639e62da116a6fbb2a93ea0c689e546b4217fc6ef90423ba2af7c30b4b23ec544b53166 ac11618621780b1bdc0de8dbe1caf9a806d4184a33293eff2 - CHECK OK!

Then you check that all the cards generated match as per their published algorithm... - CHECK OK! Everything checks out Smiley




Spendulus
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December 08, 2017, 03:00:36 AM
 #7

There are plenty of examples of "Provably Fair" blackjack... crypto-games.net has BJ on their site... the basic process works like this:
...... AFTER the hand, you will be shown the unencrypted server seed... which you can then SHA256 and prove that it matches the SHA256 hash that you were shown BEFORE the hand to prove that the site hasn't changed anything... = Provably Fair = they cannot change the results.
...

I agree and appreciate your explaining the method.
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