Coinroll.it - Dice rolling game | Instant bets | Off-the-chain | 1% House edge

[Scrat Acorns]

I won 150 bets and lost 6...  I bet on below 64000, which has a 1 in 1000 loss rate...  huh?

Your math is wrong. Below 64000 has a 2.34% loss rate.

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[Hfleer]

Coinroll is a new dice rolling game with a few interesting features:

A house edge of only 1%

Unconfirmed deposits
We accept unconfirmed transactions. You can begin playing instantly - no registration is required.

Deferred withdrawals
You can choose to have your winnings sent to an address once your deposit has cleared. Staying on the website while your transaction is queued is not necessary.

Instant bets
Bets are off-the-chain and are processed instantly while still being provably fair. As such, you can bet as low as 0.00001 BTC.

API
An easy-to-use interface is available for those who would like to use Coinroll from the command line or integrate it into their projects.

Custom games
While a few preset games are available, you can set a target number from 1 to 64000 and your win odds and multiplier will be calculated accordingly.

Here's an example of a bet. More information on provability and database dumps are available here.

A note on withdrawals: A 0.0005 miner's fee is added to all withdrawals, so the minimum balance you can withdraw from is 0.00050001 (it would result to a transaction of 1 satoshi plus the minumum fee). The fee is automatically factored into the amount when you click on Withdraw.

Betting limits will slowly be increased over the coming weeks.

Come check it out at https://coinroll.it

I won 150 bets and lost 6...  I bet on below 64000, which has a 1 in 1000 loss rate...  huh?

I just rolled 200x this bet and lost 4 times won 196, it does show you the win percentage as 97.7% in the game select area.

[smeagol]

I won 150 bets and lost 6...  I bet on below 64000, which has a 1 in 1000 loss rate...  huh?

Your math is wrong. Below 64000 has a 2.34% loss rate.

Ahhh!  MY MATH!  oops... lol
lost 60 bitcoins...

[Hfleer]

I won 150 bets and lost 6...  I bet on below 64000, which has a 1 in 1000 loss rate...  huh?

Your math is wrong. Below 64000 has a 2.34% loss rate.

Ahhh!  MY MATH!  oops... lol
lost 60 bitcoins...

ouch

[Scrat Acorns]

ouch

He is trollin'.

[smeagol]

ouch

He is trollin'.

oops! sorry! I meant 0.6 BTC... not as much of a loss but still a lot...

[Scrat Acorns]

Added a live view of all bets being played at https://coinroll.it/bets

[Hfleer]

Added a live of view of all bets being played at https://coinroll.it/bets

Over half-million bets and counting, nice.

[Zaih]

Added a live of view of all bets being played at https://coinroll.it/bets

Over half-million bets and counting, nice.

Very nice. Grats

[Namworld]

The live bets feed page is very neat.

[dooglus]

I was asked to audit the provable fairness, and did so.

I found a problem, though I don't think it's important, and can be corrected.

Take https://coinroll.it/bet/0024cd8925bf for instance.  It says the nonce was 41988, that the lucky number was 41982, and that I can verify this by running:

Code:

$ echo -n '090de7a9a363bc41c992ec000f77ffe6692155308ae5020a4e1e58c4222a1b65:41988' | openssl dgst -sha512 -hmac 'mEL0R7en4QQZtJpHkath9YtvEed2YbzrOAQrIkTkd1ZmX5YNoPprlWf6XeTFoQZD' | sed 's/^.* //' | cut -c1-4 | xargs -I{} printf "%d\n" 0x{}
56785

However, as you can see, that gives 56785 as the lucky number.  If I use 41987 as the nonce, I get the correct lucky number:

Code:

$ echo -n '090de7a9a363bc41c992ec000f77ffe6692155308ae5020a4e1e58c4222a1b65:41987' | openssl dgst -sha512 -hmac 'mEL0R7en4QQZtJpHkath9YtvEed2YbzrOAQrIkTkd1ZmX5YNoPprlWf6XeTFoQZD' | sed 's/^.* //' | cut -c1-4 | xargs -I{} printf "%d\n" 0x{}
41982

I think all that's happened is that for a few thousand bets the database recorded the wrong nonce.  If we look at the database dump, we see records for nonces 41985, 41986, 41988 (twice), 41989, etc.  41987 is missing, and 41988 was recorded twice.  https://coinroll.it/bet/abd8a11aba66 is the other time it was used.

Here are the two verification screens for the two bets.  Notice that the shell commands are identical in the two cases, but the lucky numbers they are meant to produce are different...





Edit: note that sometimes the reported nonce is off by as much as 4:

Code:

bet "04ea204f8cb5" nonce 42290 should be 42286 (off by 4)
bet "c56d77775b9e" nonce 42290 should be 42287 (off by 3)
bet "9e2e44e570c0" nonce 42290 should be 42288 (off by 2)
bet "2ec74cf218a1" nonce 42290 should be 42289 (off by 1)

bet "70cb835c740f" nonce 42299 should be 42296 (off by 3)
bet "de7c0b0ceb1d" nonce 42299 should be 42297 (off by 2)
bet "715dd2d635ee" nonce 42299 should be 42298 (off by 1)

Edit2: Note also that none of this seems to affect the fairness.  It does just seem to be an issue with the archiving of the bets, specifically the nonces.  The stored lucky number and result is correct, and presumably so was the payout.

[Namworld]

Short story:
Only the bets archive/history seems to have the wrong nonces (repeated) as viewed in archive or on the website. The lucky numbers appear to be the one that would have been generated with the correct nonce (not skipped like on the archived bets).

Ex:
https://coinroll.it/bet/26c991a300e6
Shows nonce 41875 & lucky number 45957 (Which can be generated with nonce 41874)
https://coinroll.it/bet/916f4107ff33
Shows nonce 41875 & lucky number 25074 (Which can be generated with nonce 41875)

Well that is an issue if historic bets are to be verified with a script. Although if it only impacts the archive, correcting the issue should be easy.

[dooglus]

Well that is an issue if historic bets are to be verified with a script. Although if it only impacts the archive, correcting the issue should be easy.

Yes.  I tested them all, and no nonce is off by more than 4, so it's easy to find out what the correct nonce should be.

[Scrat Acorns]

Thank you for pointing this out dooglus. I will investigate.

As you said, this only affects the archiving of the bets since it is a separate routine.

Edit: This is a concurrency bug. The lucky number calculation correctly uses the atomically incremented nonce while the archiving operation increments it by itself. This will be fixed.

[BigBitz]

Wow.

Just lost 15 in a row of the 25% chance win bet.

Brutal.

No BTC left 

[Mooshire]

If you're like me and what even payouts instead of even odds:

Less than 32440 for 2x payout

Less than 21626 for 3x payout

Less than 16220 for 4x payout

[dooglus]

Wow.

Just lost 15 in a row of the 25% chance win bet.

Brutal.

No BTC left 

That happens 1.33% of the time, so it's not that rare:

Code:

>>> (0.75**15) * 100
1.3363461010158062

[BigBitz]

Wow.

Just lost 15 in a row of the 25% chance win bet.

Brutal.

No BTC left 

That happens 1.33% of the time, so it's not that rare:

Code:

>>> (0.75**15) * 100
1.3363461010158062

lol, thanks man. Lost my last bit coins 

[Scrat Acorns]

The messed up nonces have been fixed.

[dooglus]

The messed up nonces have been fixed.

Is the db dump fixed now too?

From Wikipedia, the free encyclopedia

Nonce may refer to:

Cryptographic nonce, a number or bit string used only once, in security engineering

Nonce (slang), a British and Australian slang term for a sex offender, usually a child sexual abuser

Being British, 'nonce' always seems like unfortunate terminology...