Bitcoin Forum

Hi guys,

I've recently launched http://bitjack21.com

It's an online bitcoin blackjack game done entirely in HTML5.  It's plays beautifully in all browsers including mobile.  It uses standard casino rules:

* Dealer stands on all 17's
* Blackjack pays 3:2
* Double on any 2 cards
* Split to up to 3 hands
* Double after split (except aces)
* If aces are split, you get 1 card per hand.
* 1 "chip" is currently worth 0.01 BTC
* Minimum bet is 0.02 BTC (2 chips)
* Maximum bet will be increased later and is currently 0.75 BTC (75 chips).
* 8 decks are shuffled before every hand.

The "house edge" with this ruleset is razor thin, less than 0.5%, enjoy :)

I plan on adding roulette soon.

Thanks.

EDIT:  As of 8/9/11 I have enabled the "crypto-proof" system on the website.  This system is a mathematical PROOF that every hand you play at http://bitjack21.com is 100% completely honest.  (Technical details at http://bitjack21.com/cryptoproof )

http://i52.tinypic.com/1zyj3ts.jpg

About how long does it take for a deposit to show up?

I require 1 confirmation.

All suggestions are welcome.  Are there any stats you guys would really like to see?

Thanks!

Please stop making site like this...I loose all the Bitcoins! Fun site, should always get out when your on top.

Max bet has been increased to 0.25 BTC.

Max bet is now 0.5 BTC (it will continue to rise as we get more players).

People who have played on my site, do you have any suggestions?

OK, I have found a way to COMPLETELY, 100%, beyond any reasonable doubt, *PROVE* that my game is 100% honest.

It only seems fitting that cryptography, which is the basis for our trust in the bitcoin system, will now be used as the basis for trust in my bitcoin blackjack game.

Here's how it will work:

1.) Embedded in the client side javascript code of the game will be a random number generator.  It will generate a random number prior to each hand (call this number R2).  The user will have the option to either use the number generated by their web browser, or modify it as they see fit.

2.)  When the user clicks on "DEAL", their random number will be sent to the server.  The server will generate 2 of its own random numbers, call them R1 and RX.

3.) The server computes SHA256(R1 + RX), and sends this back to the user, this is displayed in the user's browser at the start of each hand.

4.) The server generates a very long string of random bits by calling
SHA256(R1 + R2 + 0)
SHA256(R1 + R2 + 1)
SHA256(R1 + R2 + 2)
SHA256(R1 + R2 + 3)
etc...

This string of random bits essentially *is* the deck order.  In other words, you can directly determine the order of the cards in the deck directly using this (I will be posting the function).

5.) AFTER the hand is over, the server displays to the user the actual values of R1 and RX.

This will allow the user to mathematically prove/verify that:
1.) The order of the cards was COMPLETELY RANDOM.
2.) The order of the cards was predetermined prior to the hand starting.
3.) The order of the cards did not change during the hand.

-Mr. Sizlak

Am I keeping track wrong or is it taking the bet when there's a push?

I jumped the gun, nevermind.

Edit: Any chance of surrender and/or insurance features in there?

Oh, and a hand history and win/loss ledger.

I considered offering insurance.  Then I decided it would add unneeded complexity to the code.  It is a mathematical fact that it is NEVER in your best interest to take insurance (over the long run). The only exception is if you are counting cards and the current count indicates that it is favorable to take insurance.  However, since you can't count cards in my game due to the decks being shuffled prior to every hand, then it is NEVER in your best interest to take insurance.  Now some people have told me I should offer insurance for this very reason (because it works in favor of the house).  If this is something people want then I will consider it as a future enhancement.

As for surrender, no, I will not be offering it.  The house edge with the current rules is very very thin (about 0.35%).  Blackjack also has a very high variance.  Because of these things, there are many days when I end up losing significant amounts of bitcoins, and that is why I can not add surrender.

Hand history and win loss ledger will definitely be coming soon as enhancements.

Also, as of now, I have my "crypto-proof" system turned ON.  This system *proves* that every hand you play on http://bitjack21.com is honest.  It proves that:

1.)  The order of the cards was 100% completely random.
2.)  The order of the cards was determined just before the hand started and did not change during the hand.

I have posted an informative page on the site about how the crypto-proof system works, and how you can use it to verify that any given hand was honest:
http://bitjack21.com/cryptoproof

Thanks for playing!
-Mr. Sizlak

Update 8/13/2011:

In this pic you can see crypto-proof in action:

http://i52.tinypic.com/1zyj3ts.jpg

Technical details of crypto-proof available here:  http://bitjack21.com/cryptoproof

As of right now, the min bet is 0.02 BTC and the max bet is 0.75 BTC.  I'm willing to raise the max bet but my benefactors have informed me that I need to keep a 32:1 max:min bet ratio.  In other words the max bet will always be approximately 32 times the min bet (give or take a little bit).  So I could raise the max, but I'd have to raise the min as well.  Let me know if you guys would prefer a higher max bet, and as always, thanks for playing on bitjack21.com, the only bitcoin blackjack site on the internet that GUARANTEES that every hand you play is 100% honest, 100% random, and can PROVE it!

Roulette will likely be finished by the end of September.  It will be a multiplayer system with up to 4 players per table.

I don't know much about Blackjack, but please consider the following for your Roulette game:

Multiple, configurable saved bets that can be recalled very easily
Right-click to remove mistaken bets from the table quickly (important in fast-paced multiplayer)
One button to remove all bets immediately
Euro-wheel with no 00
A private table option, instead of just public multi-player

I'll be sure to visit with most, if not all of these. :-)

Some of these features keep me away from the currently available roulette games.

Thanks!

All good ideas!

Have you tried http://bitjack21.com ?

I'm running a promo that will start at 5 AM GMT 2011-08-23 (Midnight Eastern US Time) and run for 24 hours (until midnight Eastern US time 2011-08-24).  The prizes are as follows:

2 BTC - To the player who wins the most BTC.
3 BTC - To the player who loses the most BTC.
1 BTC - To the player who plays the most hands.

I will announce the winners here after the promo is over.  If this is well received I will make it a regular occurrence.

http://bitjack21.com

i have a problem!
i've split a hand, one was busted, the other one was a 20, the dealer was busted but my net gain was 0. i'm pretty sure i was supposed to win on my good hand! it was my first hand! should I expect a lot of bugs?

L.E. it happened 2, same situation

http://i43.tinypic.com/1199m6s.png

A nice idea; good for the basic strategy player since every hand has BS odds; a few suggestions to improve your reach:

1. Strongly suggest you make your site actually render in IE9+.
2. Also strongly suggest you offer two versions of the blackjack: One where the deck is shuffled before every hand, one where the deck achieves at least 75% penetration before a reshuffle. You'll get bigger players that way, most of whom will lose money over the long term. You may need an investor for that, however :)

Other than that I may go in and play a few hands to see how it plays..

BE ADVISED:

I have attempted to contact these guys twice regarding a withdrawal, and I haven't received anything back... No contact, no coins.  At this point, I'm considering these guys as a scam.

Please respond to me if you'd like more information or to make it right...

-EP

Yup, me too.  I have 1.2 btc in there that he won't withdraw (I have contacted him 3 or 4 times).  He's a scammer!

The site was bought out by Andrew Bitcoiner and seems to have stopped paying out.

I think there was an issue where the site was letting you double-down (and possibly split, as well?) for free, which lead to people being able to make vast profits.

There are lots of posts about it in this thread:  https://bitcointalk.org/index.php?topic=39591