\[ALPHA\] FTC dice / coinflip game
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[quote name=“slavco” post=“44423” timestamp=“1387055928”]
I haven’t found any services that reveal the formula how winnings are calculated or it’s on the client side.
[/quote][url=http://ftcgames.eu/provability]http://ftcgames.eu/provability[/url] All formulas used are revealed upon calculation ;)
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If it’s only one formula for all the time then please accept my excuse, an otherwise I can give you a good reason I don’t believe it :)
BTW I believe it’s honest no intention to offence anyone ;) -
If you think from math. side revealing the server key for much more transactions / plays make probability lower for cheating. Anyway, always end users must believe that service provider is honest, at the end of the day if someone says 50% chance for winnings it’s easy to be checked as true/false after observing X transactions for the play address :)
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[quote name=“slavco” post=“45142” timestamp=“1387222521”]
If you think from math. side revealing the server key for much more transactions / plays make probability lower for cheating. Anyway, always end users must believe that service provider is honest, at the end of the day if someone says 50% chance for winnings it’s easy to be checked as true/false after observing X transactions for the play address :)
[/quote]Wrong!
It’s entirely possible to cheat users by producing equal numbers of wins/losses, but weighting the wins towards the smaller amount, while giving more losses to the larger amount. If someone says 50% chance, and demonstrates an equal number of wins to losses, this proves nothing at all.
The only way to have a provablly fair system is by exposing the formula, which is static and unchanging. Primedice.com does this, just-dice.com does this, coinroll.it does this. If it REALLY is fair, there’s no reason not to do this.
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Fair play ( There will be fairness calculator script ) :
- Your transaction id
- Game key
- number = last 4 bytes of md5(txid+key) to integer module 100
Is this honest ?
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[quote name=“slavco” post=“45213” timestamp=“1387230380”]
Fair play ( There will be fairness calculator script ) :- Your transaction id
- Game key
- number = last 4 bytes of md5(txid+key) to integer module 100
Is this honest ?
[/quote]Only if you publish the hash of the key prior to the bet, and the actual key that corresponds to that hash after the bet.
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exactly and really I found only few services that do the same. Most of them are waving with exposing the formulas and not exposing the server keys hashes. :)
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or exposing the next day => they could calculate the winnings how they want and then to calculate appropriate hash. In case of coinflip game creating such secret will have 0.5^number_of_plays probability to find.
On small number of plays it’s possible and could be performed with almost no expense, but for popular sites no need of cheating => 50% probability and 1.95 will do the job :)
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[quote name=“slavco” post=“45216” timestamp=“1387230958”]
exactly and really I found only few services that do the same. Most of them are waving with exposing the formulas and not exposing the server keys hashes. :)
[/quote]As I mentioned, Satoshi’s dice does this, so does primedice, just-dice, and coinroll. If there are others out there with the same popularity, I’ve not heard of them.
[quote author=slavco link=topic=5931.msg45219#msg45219 date=1387231441]
or exposing the next day => they could calculate the winnings how they want and then to calculate appropriate hash.
[/quote]Just-dice, Satoshi’s dice, and coinroll expose it the next day. Primedice exposes it (and changes it) after every roll.
[quote]
In case of coinflip game creating such secret will have 0.5^number_of_plays probability to find. On small number of plays it’s possible and could be performed with almost no expense, but for popular sites no need of cheating => 50% probability and 1.95 will do the job :)
[/quote]I’m not following your math. If the server keys are of a fixed size which is suitably large, I don’t see how you could cheat that.
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Simple brute force.
server keys are hashes => fixed size.
I have exposed my formula already.ok!
let say you have:
tx1 loose ; tx2 loose ; tx3 win and I claim that you have 50% probability for wining what is proven by my public formula right and applying server hash and txid.
I can generate not just one but many server side keys ( hashes ) that when applied with public formula will give exact output.
e.g. this means that I can calculate the winnings on 30% and serve you a hash that will prove that probability is really 50%.As you said, only exposing the hash of the server key before the bet and exposing the server key after the bet is the real proof that system is honest. :)
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Soooo… you’re going to brute force a 256 bit hash collision?
I’ll believe it when I see it.
If we have a “perfect” hash function with output size n, and we have p messages to hash (individual message length is not important), then probability of collision is about p2/2n+1 (this is an approximation which is valid for “small” p, i.e. substantially smaller than 2n/2). For instance, with SHA-256 (n=256) and one billion messages (p=109) then the probability is about 4.3*10 ^60.
The Bitcoin network itself produces less than 10,000,000 hashes a second. At that rate, it would take the Bitcoin network itself 1*10^53 YEARS (that’s a 1 with 53 zeros after it) to produce a hash collision.
A mass-murderer space rock happens about once every 30 million years on average. This leads to a probability of such an event occurring in the next second to about 10^15. That’s 45 orders of magnitude more probable than the SHA-256 collision. Briefly stated, if you find SHA-256 collisions likely then your priorities are wrong.
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Here, I’ll prove it to you.
I’ve picked a number at random. It’s encoding is EXACTLY 28 bytes.
Here’s the SHA-256 hash of it: fd6f52aad269c7188c44415185759929b65f80afc387a98a7fe568f9c9b5dbde
Go brute force me the number I picked. I’ll even give you the first 6 bytes: 59 6f 75 27 76 65
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Nope we are talking different things ( my wooden engrish :) )
I say if coin game service give you the formula for the bet calculation and that formula proves that 50% probability of winning based on your txid and server key that will be revealed after the play, no matters if service on the server side calculate winning probability on 30% they can give you hash that will prove that your bet is really honest calculated e.g. 50%
Or via experiment:
- I’ll create a script on special address for you ( this can be done tomorrow )
- I’ll reveal the formula used to calculate the winnings it will claim 50% chances of winning
- After your 5 bets ( you will loose them all ) I’ll give you a key to check the fairness of the script and will prove that is correct.
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[quote name=“slavco” post=“45234” timestamp=“1387234765”]
Nope we are talking different things ( my wooden engrish :) )I say if coin game service give you the formula for the bet calculation and that formula proves that 50% probability of winning based on your txid and server key that will be revealed after the play, no matters if service on the server side calculate winning probability on 30% they can give you hash that will prove that your bet is really honest calculated e.g. 50%
Or via experiment:
- I’ll create a script on special address for you ( this can be done tomorrow )
- I’ll reveal the formula used to calculate the winnings it will claim 50% chances of winning
- After your 5 bets ( you will loose them all ) I’ll give you a key to check the fairness of the script and will prove that is correct.
[/quote]
I don’t get it. You’re saying you’re going to reveal a hash of a piece of data that will be used in the calculation, and then after the rolls, you’ll produce a DIFFERENT piece of data that when hashed result in the SAME previously revealed hash, that will result in the same rolls as what was produced?
This I gotta see.
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I’m saying that If I reveal the hash of the server key before bet I must be honest. ( the same as you say )
but If I’m revealing only the server key ( no matter what form it is ) after the play and not revealing server key hash before the play then I could cheat :) -
[quote name=“slavco” post=“45239” timestamp=“1387235530”]
I’m saying that If I reveal the hash of the server key before bet I must be honest. ( the same as you say )
but If I’m revealing only the server key ( no matter what form it is ) after the play and not revealing server key hash before the play then I could cheat :)
[/quote]Well then I’m not sure why were’re debating this. All the sites I listed reveal their server key prior to play. That’s the only way to make it fair.
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They reveal server seed not secret. As i understand secret is revealed after the play
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[quote name=“slavco” post=“45243” timestamp=“1387236020”]
They reveal server seed not secret. As i understand secret is revealed after the play
[/quote]They reveal the hash of the server secret. Afterwords, they reveal the secret. I can take the secret, and hash it myself, and compare it to the hash they showed.
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Yup, that’s the only way fairness is calculated (server key hash before and server key after ) and on big number plays per day def. the margin is the only one that ensures the profit. :)
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any amount to test ? I have 0 ftc at the moment . my adress is below.I will play as soonas possible