Can anybody stall Bitcoin for 72BTC per hour? ANSWER: NO

[phelix]

typical tx fee is 0.005 btc
https://en.bitcoin.it/wiki/Transaction_fees

~2400 txs fit into a block
http://bitcoin.stackexchange.com/questions/1747/bitcoin-block-size-what-are-the-rules

2400 * 0.0050001 * 6 blocks/hour  ~=   72

Miners will choose the tx with the highest fees. But to be really sure I just create 3000 tx with a fee of 0.011 every ten minutes. 33 BTC edit: 198 BTC

is that really all it takes?


Of course clients can increase fees. It would take time and user effort, though. I think with some clients it is not even possible for the user.


 

[grue]

fees get exponentially higher as the block fills up, so your fee assumption is wrong

[phelix]

fees get exponentially higher as the block fills up, so your fee assumption is wrong

hmm, could you please elaborate or give a link? you make it sound like there is some automatic system to do that but I never heard of that.

Would that be the case if I would do it right now?

[FreeMoney]

So someone spends 72/hr in order to make people pay .001 for tx? That sounds wonderful for miners and a tiny inconvenience for users. It's just ~1.5M dollars worth per month. Assuming you don't drive prices up at all.

[phelix]

So someone spends 72/hr in order to make people pay .001 for tx? That sounds wonderful for miners and a tiny inconvenience for users. It's just ~1.5M dollars worth per month. Assuming you don't drive prices up at all.

the establishment has plenty of dollars. also they can always print more


imagine bitcoin will stall for three days.

[FreeMoney]

So someone spends 72/hr in order to make people pay .001 for tx? That sounds wonderful for miners and a tiny inconvenience for users. It's just ~1.5M dollars worth per month. Assuming you don't drive prices up at all.

the establishment has plenty of dollars. also they can always print more


imagine bitcoin will stall for three days.

I suppose a short term inconvenience would not be too hard to pull off this way, but they would be supporting the bitcoin price and enriching bitcoin miners. An the public relations angle would be bad but not terrible, "Why am I not getting in a block?" Someone else is paying more than you.

Solutions exist and more will be made regarding setting your own fee and even replacing transactions to have a higher fee when they  don't get confirmed fast enough. So this is expensive, just an inconvenience, and going to become less effective over time even if the block size is not increased, which it probably will be.

[Bit_Happy]

Double F.U.D.
Can the network even handle a large volume of legit transactions?

[Bit_Happy]

Triple F.U.D.
Transactions take too long, Litecoins will become supreme?

[phelix]

So someone spends 72/hr in order to make people pay .001 for tx? That sounds wonderful for miners and a tiny inconvenience for users. It's just ~1.5M dollars worth per month. Assuming you don't drive prices up at all.

the establishment has plenty of dollars. also they can always print more


imagine bitcoin will stall for three days.

I suppose a short term inconvenience would not be too hard to pull off this way, but they would be supporting the bitcoin price and enriching bitcoin miners. An the public relations angle would be bad but not terrible, "Why am I not getting in a block?" Someone else is paying more than you.

Solutions exist and more will be made regarding setting your own fee and even replacing transactions to have a higher fee when they  don't get confirmed fast enough. So this is expensive, just an inconvenience, and going to become less effective over time even if the block size is not increased, which it probably will be.

media would eat us alive like vultures. imagine all tx would go to an address that is known to be connected with highly illegal activity.

mobile clients would basically stop working.

[phelix]

ebay's market cap is ~ $87189480000 PayPal ~ 1/3  =  $29063160000 = mc

198btc  *  24h * 365days * 35$/btc  =   60706800    ~=  mc * 0.2%

if I got it right paypal could stall bitcoin for a year at 0.2% of their market cap.

even worse, as price would fall stalling would become cheaper. guessed cost to run her into the ground: $100,000

As bitcoin price would drop they could even profit from it (going short).


I always hate when I realize something disturbing about Bitcoin.

[btcusr]

typical tx fee is 0.005 btc
https://en.bitcoin.it/wiki/Transaction_fees

~2400 txs fit into a block
http://bitcoin.stackexchange.com/questions/1747/bitcoin-block-size-what-are-the-rules

2400 * 0.0050001 * 6 blocks/hour  ~=   72

Miners will choose the tx with the highest fees. But to be really sure I just create 3000 tx with a fee of 0.011 every ten minutes. 33 BTC edit: 198 BTC

is that really all it takes?


Of course clients can increase fees. It would take time and user effort, though. I think with some clients it is not even possible for the user.


 

That's so evil. Such adjustments could encourage mining but not now.  

[DeathAndTaxes]

There is no such thing as stall.  People would pay higher fees and life would go on.  This tactic however would massively enrich miners and cause a boom to the exchange rate. 

[goatpig]

ebay's market cap is ~ $87189480000 PayPal ~ 1/3  =  $29063160000 = mc

198btc  *  24h * 365days * 35$/btc  =   60706800    ~=  mc * 0.2%

if I got it right paypal could stall bitcoin for a year at 0.2% of their market cap.

even worse, as price would fall stalling would become cheaper. guessed cost to run her into the ground: $100,000

As bitcoin price would drop they could even profit from it (going short).


I always hate when I realize something disturbing about Bitcoin.

You don't understand the mechanics of Bitcoin. Your assumption is that tx fees will remain static. Bitcoin is built to function without the coinbase reward, only on tx fees. Competition for tx fees is natural and already part of the system. This isn't an attack, it's just using Bitcoin as intented. The more transactions are processed, the more expensive spots in blocks get. This "attack" would only increase the BTC/$ exchange rate at an exponential rate.

Simple example: Assume that your attacker emits 2400 tx per block with an 0.005 fee. It is fair to say this would increase the minimum fee by 0.001 BTC, as anyone who wants to get his tx through would just pay 0.006. Now assume the attacker is a lunatic and is going to fill his next tx batch with the new min fee. He would essentially increase the fee by 0.001 BTC per block, on every block. A week down the road, the fee would be about 0.15 BTC and this guy would need about 50k BTC a day just to fill the blocks.

This practice would have 2 effect: First, he would the biggest consumer (read: supporter) of BTC out there. After a couple weeks of this stupidity, the "attacker" would represent 90% of daily BTC trade volume, pumping the market cap up 10 folds.

Second, I doubt anyone with a meaningful BTC tx would be afraid of even a 0.5 BTC fee. You were talking about Paypal. Their fee is like 5% per transaction. That would be a tx as small as 10BTC with a 0.5BTC fee. However, a 0.5BTC fee implies the attacker needs 170k BTC a day to pull his little trick. With such a big buyer, we'll break $500/BTC easily and it would cost him short of $100mil to pull his move on a daily basis.

[laughingbear]

I am not worried about anyone buying 72 btc every hour on the hour, and then giving it away to miners, hell... I encourage it!

[misterbigg]

I guess if you're willing to spend close to $2 million USD a month to "stall" Bitcoin then yeah it would work but I would love to be a miner in that scenario.

[btcusr]

yes, that's about 1,734,480 BTC a year.
@ 50 USD exchange rate per BTC, it would be $86,724,000 a year

[qwk]

I think most of the posters in this thread are missing the point, really.

Of course, the bitcoin protocol itself is in no way endangered.
And of course, the default client and probably most full-blown implementations of alternative clients can easily cope with said "attack".

But if somebody with the money and the motivation really pulled this of for, say, a week, here's what i believe would happen:

- people with only tiny amounts of bitcoins would not be able to experiment with it, because they could not afford the fees.
- people with implementations of a client that does not let them adjust the transaction fee would be unable to spend their coins.
- people with a high volume of transactions of small size would face a huge increase in costs.
- Satoshi Dice ... hmmm, i wonder ... but actually, i don't care.

After a few hours, it'd be field day for haters on slashdot etc.
A few days, the media.
Weeks, the bitcoin "community".

The miners might have fun for a day or two, but then?


All in all, once the dust settles, it'd not be the end of bitcoin.
But it might very well be a setback of at least the same impact as the MtGox hack.


So, what's the conclusion? Check each and every implementation of bitcoin clients, be they online wallets, mobile apps, lightweight, heavyweight, whatever applications for one thing:

Is the user able to adjust the transaction fee? If not, fix this.
This should be "best common practice" for all developers of bitcoin clients.

[GoldenWings91]

Such an 'attack' would make the price of BTC skyrocket. In order to sustain this 'attack' a lot of bitcoins would need to be purchased. The laws of supply and demand dictates if there is a limited supply and a large demand price will go up. At 72BTC needed per hour the demand for BTC would be enormous. The longer this 'attack' lasts the more bitcoins are in demand the more expensive they become. This would make such an attack unsustainable for even the richest entities. Even though transactions won't be able to process for a while I doubt anybody would complain when seeing the value of their bitcoins skyrocketing.

[Gavin Andresen]

The default block-filling algorithm that most miners are running is:

+ Fill up part of the block with the highest transactions, regardless of fees
+ Then fill up the rest of the block with as many fee-paying transactions as possible, highest fee-per-kilobyte first.

... so flooding the network with high-fee transactions won't "stall Bitcoin."  Well, except for people playing SatoshiDice or doing something else that results in lots of low-priority fee-paying transactions (and even there, they could always opt to pay a little more in transaction fees).

[phelix]

The default block-filling algorithm that most miners are running is:

+ Fill up part of the block with the highest transactions, regardless of fees
+ Then fill up the rest of the block with as many fee-paying transactions as possible, highest fee-per-kilobyte first.

... so flooding the network with high-fee transactions won't "stall Bitcoin."  Well, except for people playing SatoshiDice or doing something else that results in lots of low-priority fee-paying transactions (and even there, they could always opt to pay a little more in transaction fees).

I guess you mean "highest priority transactions".

Glad to hear that. It makes the attack mostly pointless. Hope miners will keep up that policy.


I am always happy when something I thought could be a problem for Bitcoin turns out not to. 


Still, as qwk suggests, it would be good to be able to modify fees in every client. A notification to the user that the payment was delayed with a question if the fee should be raised might be nice.