Bitcoin Forum

Hello,
Is it advisable
wait for one confirmation before accept the payment?

Anything that can happen after the firat confirmation?

You would be advised to wait for *at least* 1 confirmation to be safe from a double spend.

But even 1 confirmation isn't a *guarantee* as a re-org can (and frequently does) occur in which case a double spend could still occur (although this is not very likely).

The best advice would be to determine the # of confirmations based upon what you are selling. If it is some sort of internet service (such as a VPS or VPN) then there is basically no risk (as you can always just switch it off if the payment doesn't finally confirm) and if it is small goods (such as a cup of coffee) then the very small risk of a double spend after 1 confirmation would be worth it, however, it is a *house* that you are selling then I would be waiting for the recommended 6 confirmations *just to be sure*.

Thx, as you may know from a previous post of mine i asked because of a game.

People buy - only confirmed payments accepted

So would be 1 confirmation enough?
How long does 1 confirm approximately takes?

Thx

As ciyam said if you are taking automatic payments, wait for atleast 1-6 confirmations, If you are taking manual payments, you can check senders bitcoin address if he did double spend or not.

That will depend on a number of factors.    For an online gambling site in which the player's identity isn't known, then there is a potential to profit from double spending.  If there could be thousands of dollars to gain from double spending a payment that already had one confirmation against you then know eventually someone will succeed when attempting that. 

The reason retail merchants can today accept a bitcoin with no confirmations or just one confirmation is because there is little or no profit potential in attempting to double spend, and the customer isn't anonymous if making a purchase in-person.   For instance, you won't double spend your dinner tab without the restaurant being able to remember who you are.  And since double spends attempts frequently fail if you have to make ten attempts before attempt eleven is successful then the restaurant still makes a profit when averaging the one free meal among eleven visits in total.

SatoshiDICE protects against this by including in the payout funds from the wager transaction itself.  Thus if the wager never reaches six confirmations neither will the payout transaction.

The challenge though is to not let the game player know if the wager was a winner or not until after at least one confirmation.  SatoshiDICE holds off on this for some wagers until there is a confirmation so that a player isn't trying to double spend the losing wagers.