Any idea how stripe is handling confirmations? (I'm a bitcoin newbie, but I know that consensus took a minute or so the last time I had done anything with BTC.) Has that changed?
(Christian from Stripe here.) We credit USD to our user's account when we see a transaction that we believe will become confirmed. The time-delay between when the customer pushes the transaction and when we notify our users is typically less than 15 seconds and almost always less than 60 seconds.
Has the technology changed/evolved enough that that's credible? I was under the impression that it wasn't "fully confirmed" by the network until a new block was mined, or you could have double spend attacks?
Really the key question is: if a transaction that you believe will become confirmed, turns out to be invalid, who wears that? Stripe, or me? Will Stripe eat that, or will I get hit with the difference?
It's a good question. We want Bitcoin acceptance to be straightforward for our users, so we deal with a failed confirmation on our side. We do not debit the user.
I suspect this is the reason Bitpay is able to waive fees completely: they do not take responsibility for unconfirmed transactions.
> Note: Regardless of the transaction speed settings, a fully paid invoice is credited to your merchant account after the transaction has accrued six confirmations. [1]
The problem isn't detecting whether 99% of transactions will confirm.
The problem is preventing someone from ordering $10,000 worth of gold from a site that uses Stripe with Bitcoin payments enabled. Sending a paying transaction to Stripe, who confirms it within a minute, and simultaneously mining a block with contains a transaction that double spends the bitcoins sent to Stripe.
Stripe is now out $10,000. You receive your gold, sell it to your local bullion dealer for $9,500.
Of course, for Stripe, there are various hackish ways around this problem, like defining a maximum amount of, say, $1000, so that the above attack requires the attacker to mine 10 blocks instead of 1 (ie. repeat the procedure 10 times), in order to earn $10,000.
But they don't really solve the fundamental problem of accepting unconfirmed Bitcoin transactions.
It costs 80 million dollars to buy all the hardware to mine a single block. It will probably costs 800 million dollars to amass enough computing power to mine 10 blocks. It only makes sense to double spend a transaction with a VERY large amount. No transaction going through stripe will qualify.
