Bitcoin Forum

If I am right, a transaction will be safe from double spending when there are 6-7+ confirmations. On most gambling sites you can withdraw your Bitcoins with 2-3 confirmations, how can this be safe from double spending for gamble site..?

6 confirmations used to be normal seems to be getting less and less now. Risk with them I guess..

In theory, a transaction is never safe from double-spending. More confirmations decrease the chance for an attacker to succeed. The success chance will depend not only on the number of confirmations, but also on the hashpower controlled by the attacker. The chance will never be 0 and if the attacker controls more than half the hashrate of the network, his success chance at performing double spends is 100% (if he chooses to do so).

In practice, performing a double spend against 6 confirmations is exceptionally unlikely. Also, 6 confirmations takes approximately 1 hour, so that makes it a convenient guideline. However, unless you're working with large amounts of coins, 1-3 confirmations is typically just fine, as the chance for an attack to succeed is still rather low and it is not economical for attackers to try and double spend these transactions, since they lose out potential mining rewards by trying to construct a competing blockchain.

Aah I see, but I think its weird to lower your confirmations just for lower amounts of bitcoins. You can double spend a lot of small amounts than. A lot of small amounts ends up with a big amount. Or do I miss something?

There is always a risk for double spending but It's very low so you just don't think about It.

Oke, but there is a reason for waiting on 6-7 confirmations right?

I believe "6 confirmations" is used just because it takes on average an whole hour (a nice number) to get there, and there is nothing special about the number "6".
IMHO, if you are not doing a big transaction, 1 or 2 confirmations are good enough. :)

That was an exceedingly lucid and wonderful explanation.  The only think I can add is that there's something of "tradition" to this as well.  However, Rannasha makes a very good point about the link between the amount of btc and the risk-to-reward ratio of trying to pull of the double spend.

No 6 transactions is not a hard limit. It is all about risk, the more transactions the harder it is to double spend. 6 is deemed an 'acceptable' level of security but it is still possible to double spend 6 confirmations. Only 120+ confirmations is truly safe.

At Cloudbet, we allow withdrawals once all deposits have received 3 confirmations.

DirectBet pays out winnings once there is 1 confirmation for the initial bet transfer. We prefer to pay you out as quickly as possible.

Just-Dice ran for a year, and in that time we never once saw any double-spend attacks.

We had a few deposits that never confirmed, but since we never credited deposits until they were confirmed, that wasn't a problem.

The reason for allowing players to withdraw with less than 6 confirmations on their deposit is that they like it that way, and the risk of a double-spend seems to be pretty small.

Same for SatoshiBet

I remember PD had 6-7 confirmations before until recently. Extremely annoying to wait, and not worth losing the potential customers the casino might've lost.

PD has had instant deposits for a long time, they have changed to 1 confirmation one month ago after double spends. People sent transactions without fees and if they win the bet the let the transaction if not they try to send it to other wallet paying fee or using bitundo.

That was the main reason I played there and not JD, when it switched to 1 confo JD was definitely the better option. Now the only site with zero confo deposits is 999dice :(

THE DOOGLAS HAS SPOKEN

I think coinroyale has instant deposit too

Coinroyale is a terrible scamming site. Never play there.

Not really sure about the details, but 999dice was accused of scamming and the owner has left bitcointalk since Jan...
https://bitcointalk.org/index.php?topic=523178.0

It always seemed to me that accepting 0-conf deposits was asking for trouble.

The difference between 0 and 1 confirmation is much more significant than between 1 and 2.

You remember how Seuntjie had a list full of "trusted" (really I should say "regulars"or "non-beggars") that were eligible for rain. What about a trusted list for regulars who the admin can risk giving the option for 0-conf deposits to. PD3 should have sometihng like that, it's worth suggesting to Stunna. Instant deposits AND cashouts would be amazing.

Never underestimate how much effort a scammer will go to in order to rip you off.

If you need to spend 100 hours on the site to "level up" enough to be trusted with 0-conf deposits, then that's what they'll do.

Remember the 0-confi deposits from inputs.io ? :(

Also, 0-conf is just retarded, it is so easy to doublespend in 10 minutes...

That's different. Making transfers off-chain requires no confirmations so long as you trust the person offering the off-chain service.

Unfortunately in the case of inputs.io such trust would have been misplaced.

What issues were you having with CoinRoyale?

We've been in operation for close to a year. All of our games are provably fair and vetted by reputable forum members and reviewers (we even have an extensive page to explain our algorithm: https://coinroyale.com/provablyfair).

And yes, all of our deposits are processed instantly and withdrawals are instant too after 1 confirmation.