Bitcoin Forum

Introduction :
Recently a lot of new Player vs Player sites have been opening up in the Bitcoin gambling scene.
Which is great, I've personally been a huge advocate for PvP to come into popularity with Bitcoin gambling, however it's still important to be cautious.
Many sites claim to have a provably fair system, when in fact they don't. Provably fair implies the user's bets are backed by math, not the casinos word to be fair.

Problem :
We'll start with a very basic coinflip between two users example.
False provable fairness PvP :
> User Satoshi creates his game for 1BTC
> Server displays hash beneath the users game which contains {Winner,RandomString}
> User Nakamoto joins the game for 1BTC
> Server reveals RandomString + Winner

Everything may seem to check out here, the hash was displayed at the start meaning it can't be manipulated, right?
Correct, however it's not manipulation that's the point of failure here, it's the casinos knowledge.

The casino generated the winner themselves, meaning in theory they could know if the game Satoshi created would be a win for whoever joined, or a loss.
The casino could also generate their own name under a different pseudonym, and create one in which is a win for themselves while still providing the hash in the beginning.

Solution  :
External source of random of which is determined beforehand but not known by the user or the casino.
For sake of simplicity, I'll illustrate an easy way to implement this.

>User Satoshi creates his game for 1BTC
>User Nakamoto joins the game for 1BTC
>Server gets the current highest bitcoin block + 1 and displays this block to both users to verify its unmined
>Once the block is mined, the server uses the binary of the blocks hash to determine the winnner (i.e 0 = Heads 1 = Tails)

This ensures several things :
1. Transparent and verifiable still by both parties
2. Impossible for casino to manipulate results
3. Predetermined games with still and unknown result by both the player and casino


This may seem very trivial and obvious to a lot of you, however I've seen far too many people confusing fancy hashing and the term
provably fair being thrown around, when in fact the PvP site is not provably fair and essentially has a useless system in place for it.

No need to use 3rd-party information. Imo if you want to make a gambling site, you should be able to make your own RNG on your site.
We made a provably fair RNG on our site without 3rd party software or offsite information. https://www.youtube.com/watch?v=OAmSAvmvA70

I saw sites even use Random.org as their RNG lol. Well if there are any questions i will be glad to answer them. :)

If the solution would be for both parties to join first before checking the hash or the number of blocks before getting into the game maybe it will be for the best, but first I thought that this player VS player games was based on skills why it needs a flip of a coin for an RNG results I think in my opinion if I am correct I guess is to abolish all Random results and make a skill base games may be a player VS player games that may be based on just skill of a player and not all about RNG only.

The main problem in Player Vs Player online match is that you never know if the other player is the real player or it is someone from the gambling site pretending to be the player. In the latter case, if gambling site introduce a fake player, the advantage straight away goes to the online casino.

This is the primary reason why we dont see any PvP game that comes popular because of this matter.House itself can possibly make an account to battle up with their users.
Theres no way on how to verify or detect if players are part of the house or not.We have seen several pvp gambling sites in the past but as usual they do end up dying or no players at all. Coinflip or any related or similar games doesnt really attract too much players.

The OP is trying to give solution for pvp based game, as long as the game is provably fair then there is no need to worry about the fake users. Even if the admin of the site pretend to be a player then it wont be a problem because once a game is provably fair then anyone wont be able to manipulate the result or knowing the result before the game starts.

I think that gamblers who prefer pvp games are more keen to play poker or blackjack rather than a coin flip game of luck.I personally would like a lot more to play poker against other people rather than playing coin flip against another person but that just is different tastes.

As for the solution a trusted third party software should be a good start,the casino should not know anything otherwise is not provable fair.

But very few people will reach to that extent of verifying it thru a trusted 3rd party software.
Many will ask how provable fairness is done to that site and how they can verify their seed and so on and so forth and stop on this step.
And in this regard, for most pvp games, I believe we always think that deep inside there is some kind of loophole going on.
And yes, maybe that is one important factor why we really can't see a successful pvp gambling website, aside from the common problem of getting players on the site.

That can be countered if the other user is registered on the website and is active on the chat server or any form of discussion platform provided by the casino.

There should be an option for the user to decide whom to play with, apart from the casino deciding the opponent. This will insure that you are playing with an actual human.

Agreed, there is more chances for someone from the gambling house to pretend to be the player. In this case it is hard to win against the player that's been allocated by the gambling house. To keep up the reputation gained gambling houses won't get into such kind of stuffs cheating the participants and kick them with zero profiting.

There's no difference in playing with an actual human vs playing against someone from the gambling site pretending to be one of the player. And I think the only way you can recognize them is through chat but this doesn't mean that you are not against with one of the player from the gambling site.

Yup, exactly.
The solution we implemented is the one in our thread above, using unmined EOS blocks which has very little delay (~500MS Block time avg)
While still giving the users a few seconds to check that the block isn't mined if they want to.
Additionally after the game is over you're provided a tool to draw the winner from any previous hash and verify on jsfiddle / any third party

Thanks for sharing. Yeah it's a reason to be cautious. I think if the game starts after both the parties have joined or as in the hash might be changed with the control of either of the players choice, that would be beneficial. But it will be really complicated in that sense as well.

That's a bold statement Sir. But if you know gambling platforms cheating users you have to name them here, otherwise you're a kind of accomplice. Why don't you give any name here? I don't understand what you're afraid of? It would be more easy to understand what you're talking about  precisely ::)
But if I understand correctly your explanations another solution could be to hash a listing of the numbers of the next winners and to show it after several games.
For example :
Game 1 : First player
Game 2 : Second player
Game 3 : no winner
...

The problem is that most players aren't smart enough to detect when there is a flaw in the provably fair schemes or algorithms.
Most of them will be satisfied by reading the magic words "Provably Fair Game" and a page full of BS like hash, id, secret...
I am persuaded that 90% of users will not realize that the example you posted isn't fair.

I myself cannot confirm detail by detail whether a gambling site claiming to be provably fair is indeed provably fair. Although a lot of crypto casinos such as Bitsler, Bitdice, Cryptogames, Primedice, and many more provide verifiers for each user to know whether each and every roll result is truly fair, how many of us actually care to use these verifiers? And to those who are interested enough to use them and want to confirm provable fairness themselves, how many of them actually understands how all of it works?

That's because most gamblers don't see the need to understand the algorithms and logic behind a certain process. And I don't blame them. In the first place, gambling was supposed to be a way to earn profit while having fun or releasing stress every now and then after all.

It's also very difficult to prove the effectiveness of certain gambling sites since most users don't even bother researching about them and even if they do, at times, they at times get the wrong information due to spammers spreading information that a scam site is a legit one.

These kinds of posts are very helpful yet most likely go unnoticed by beginners or newbies since they basically don't understand it. They may try to read it, but it is way too difficult to understand without the prior knowledge of some of the technicalities behind the logic.

a small bump.
This is a must read thread for all gamblers but as you said but it doesn't get enough attention.
Some useless threads get hundreds of views and replies which make me wonder if gamblers really care about where they spend their money.

Especially that PvP games are now becoming popular in the gambling business.  More and more sites are now offering this kind of game so the players should know beforehand what's in store for them for this type of gambling. We always look for provable fairness system but we need to know how this really works in PvP system. Spare some time what the OP has presented and assess on your own whenever you encounter a PvP game site. And why this type of game is not attracting many players in the long run?

It's true. We will never know that your enemy in the match might be one of the site's team. In my point of view, player vs player game is enjoyable since your opponent is another player same as you but games like this have a catch as you have said. If it is a fake player then it's in favor of the site itself.

Here is solution.

User Satoshi generates random string (secret #1).
User Satoshi creates a game and sends hash of secret #1.
User Nakamoto generates random string (secret #2).
User Nakamoto joins the game and sends hash of secret #2.
Both players receives opponent's hash and sends its secrets.
Server calculates winner based on both secrets.

A player who has not sended his secret loses.

Also it may make sense to add an additional secret and hash from the server.

Thanks for the tip op. Majority of these PvP gambling sites are usually poker sites, but most of the players were bots and I was aware of that though I thought that the provably fair mechanism used by the site eased my worries. Looks like I was wrong.

Agreed. I had to read the solution proposed by op twice to fully understand it and I graduated with a CS degree. These threads definitely deserve more attention.

That's alarming indeed. What OP is exposing here is reality, it can't be denied that we ever knew who's on the other side, if that's a real player or another dummy from the site itself. the configurations that allows the house to be the winner will always favorable with the owner itself. There's should be a clear information like this in order to track if you are betting with someone and not with the dummy alone.