Quote from: cypherblock on June 11, 2014, 10:10:10 AM

Quote from: nanonano on June 10, 2014, 12:39:42 PM

What kind of adoption is held back with 10min block time versus 2.5 minute block time?

everyday in-shop purchases shops can accept non-confirmed transactions -- the risk when handled properly is minimal compared to things like counterfeit cash or credit back claims

Let's say you are buying $250 at grocery store. Really they are going to accept 0 or 1 confirmation? Chances are they will want 6 or more. It is a definite issue in my mind.

Best solution I've seen is to use trusted 3rd parties using 2 of 2 multisig transactions (greenaddress.it is rolling this out now I think). This then allows merchant to accept 0 confirmation transactions and trusts that the 3rd party won't double spend. Both merchant and customer have to be using the same 3rd party though, so that is a drawback but merchants could accept payments from multiple 3rd parties.

Steps:

Customer can send funds in advance to a multisig address requiring their signature and 3rd party sig.
At payment time, customer and 3rd party both sign a transaction spending the multisig transaction and sending payment to the merchant.
Merchant is trusting 3rd party not to double spend.
Merchant gets sent copy of transaction presumably using payment protocol, so they don't even wait for it to get propagated through the bitcoin network.

If the grocery store requires 6 confirmations, even 6*2.5=15 minutes is absolutely not acceptable, as VISA takes only 15 seconds

To compete with VISA, the block space has to be something like 2.5 seconds, which obviously won't work.

Yes, the 3rd party green address is the best solution.