Bitcoin Forum

See https://blockchain.info/charts/avg-confirmation-time (https://blockchain.info/charts/avg-confirmation-time).

Does anyone know why that is? Could this due to Bitcoin Core 0.9.0?

It is indeed related to the increasing total network hashrate.

https://bitcoinwisdom.com/bitcoin/difficulty

Bitcoin Difficulty:    5,006,860,589
Estimated Next Difficulty:    6,135,992,123 (+22.55%)
Adjust time:    After 158 Blocks, About 20.9 hours

Block Generation Time(?):    
1 block: 7.9 minutes
3 blocks: 23.8 minutes
6 blocks: 47.6 minutes


With blocks being found at a faster rate (on average), transaction will get confirmed at a faster rate (on average).

Average confirmation time of ~10 minutes is still quite significant. Won't cause any problem for the online shoppers. But people who want to use BTC for retail shopping won't be able to do it.

Yes, due to 0.9.

This is a good thing right?

Retail transactions are routinely performed at 0 confirmations, because transaction propagation alone validates any given transaction better than any other payment method in existence already. 10 minute blocks being a hindrance to retail application is the biggest myth that absolutely refuses to die.

Could the fact that the number of transactions/day is decreasing play a role in this?
(There's about 10-20% less now than in March: https://blockchain.info/en/charts/n-transactions (https://blockchain.info/en/charts/n-transactions))
There's still quite more than there was in January and February though.

Except as a business owner I'm not giving you ANYTHING till I see 3 confirmations.

There's only two things that can change the confirmation time:
1. The current fork uses a slightly modified code that has smaller target that gives faster confirmations.
2. The hash rate increased rapidly and it will take a little time for the difficulty to adjust to set the average block to 10 minutes.

In this case it's for sure (2) that is the answer.

atm, be prepared for hours to get 3 confirmations.

The hash rate hasn't jumped recently. (https://blockchain.info/charts/hash-rate?showDataPoints=false&timespan=&show_header=true&daysAverageString=7&scale=1&address=) On a log scale, it's been a straight line since the beginning of 2013, when ASICs started coming on line.

Well you are free to do as you please. But try sending me coins with correct fees but no confirmation and then try taking them back.

3.  Block are larger and the average number of blocks that a transaction has to wait before confirmation has been reduced.

v0.9 changed the defaults for block size.  The chart is not showing the average time between blocks it is showing the average time to the first confirmation of a transaction.  There is a difference.  The average time between blocks has been significantly less than 10 minutes for months now.

Then have fun losing business to competitors that do accept 0-conf transactions and still see 0 to almost 0 losses due to double-spends.

edit: for brick-and-mortar stores and other business that relies on instant delivery of goods that is. Everything that is bought online but has to be physically shipped can afford to wait for one or more confirmations.

There is really no need for that. Once you see the transaction go through, even without confirmations, you are safe.
The transaction will end up going through...there is no way for the purchaser to reverse it once you see it show up.

OK, I thought that having 51% of the hashing power allows you to do just that and more....

Exactly! Since nobody controls or will control 51% of the hashing power, there is no fear for a business owner.

You could double spend the transaction.

If you control 10% of the hash power, you can replace the Tx in your mempool with one that overrides the existing one. It'll have a 10% chance of working.

no!

the miners are adding more hash power everyday, to exceed the difficulty causing them to be able to mine faster then average. the difficulty tries to rise high enough to compensate, but more hash power keeps getting added on.. nothing at all related to the client program at all.. its miner related

One could theoretically create an app that first sends out the payment to the merchant's address. But immediately after that also sends the same to 50 other addresses too. I think there is a chance one of those 50 will get confirmed and the merchant could end up with nothing. Is this possible?

Lol at BTC which claims 15 minutes transactions.  I remember my first ever BTC purchase and it took over 8 hours for the coins to be confirmed.  Not sure why people think BTC can't be replaced by something better.

Well then you are going to lose customers to other businesses that are smart and realize there is no point to wait for a confirmation.

Who controls even 10% of the hashpower??

And why would you risk losing your 25 bitcoin block reward just to have a small chance of double-spending some satoshi at your local starbucks, lol.

Any amount of money that would be comparable to the current block reward (25 btc) would wait for one confirmation at least.

Double spending <<1 BTC isn't worth the pain it would take to have the small chance of succeeding.

Do you remember when grocery stores used to cash checks for you so you could do your shopping? People defrauded them all the time and they'd put up your picture and never accept checks from you again. It was part of the cost of doing business but brought in a lot of customers because it was convenient.

 

It's possible but the merchant would see the duplicate transactions almost immediately. And then one transaction would very very quickly spread over the network kicking the other ones out, I believe.

The way to successfully double spend is to submit the transaction at two different nodes very far from each other. Even then, you only have seconds at most to grab the merchandise and run before the merchant notices the double spend. And you only have a 50/50 chance of it succeeding. And that is also assuming the merchant isn't very well connected to the bitcoin network. It isn't easy to do in practice, for small transactions it doesn't even matter, and usually will be noticed by the merchant.

That will be good. But there is a risk of double-spending.


Hmm.... So you will tell your customers to wait for half an hour until you get those confirmations?

If the correct fee is attached this generally doesn't happen.

There is essentially 0 risk of double-spending, because even trying to do something like this requires what amounts to a very sophisticated Sybil attack whereby you've essentially ostracized the retailer's node from seeing your double spend long enough for that double spend to beat your original transaction in network propagation.

The chance of success is completely probabilistic in nature and extremely remote, and the moment we're talking about an amount of value where that even remotely becomes worth pursuing, now we're in the realm of waiting for confs, and that entire vector of attack goes out the window the moment a single conf even happens.

Are you serious?

The majority of the hash power is concentrated in pools that control > 10% of the hash power.

There's also no risk losing your 25 btc block reward. All you're doing is replacing a tx in the mempool with a different tx.

And if this were done, it wouldn't be done to scam starbux outta a $3 coffee. Someone could buy thousands of dollars worth of stuff at best buy and do it.

Assuming that you already had 51% control of the network, and at the current rate of $3 per GH/s for modern mining equipment, it would require about 15 million USD a week to maintain 51% control.   An entity that was large enough to have the initial capital and maintain that kind of cash flow is probably not going to be in the business of defrauding retail bitcoin transactions.