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Author Topic: The cost of fast confirmation, OR, "Turbo Mode"  (Read 1545 times)
vess
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August 11, 2010, 05:46:18 PM
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I was thinking today about the cost of speeding up the time to get, say 5 blocks generated if one was impatient for a purchase to be confirmed.

So, I rented a server at voxel.net, which claims to cost one third what amazon does, and I ran bitcoin for a bit to see what it could do there, per core.

Results: about 1000 kh/s per core. (Note, I expected double or triple based on their marketing. Some tuning could probably be done here.)

Incidentally, this implies cost per minted BTC of (at current difficulty of 354): $.1/hr for roughly 17.5 days = $42 per 50 BC = $.84 per BTC. Ouch!

But, let's imagine I want to double up the speed of the network to get my transaction going quickly. I would then need approximately 2.5 million kh/s, or about 2,500 servers. This would get me roughly one block per 10 minutes. Combined with the rest of the network, we'd be double-timing blocks, or getting one out every five minutes. Of course, I'd only need to do this for about 25 minutes to get my five blocks.

So, 2,500 servers * .42 hours = 1,041 hours * $.10 = $104.10. Less the current value of the 250 BTC at $.06  = -$15: Net cost is $90 to get the transaction sped up.

If you wanted the confirmation in 10 minutes, you'd need four blocks plus the network's blocks, so you'd need roughly 10,000 servers, but of course, they'd take less time:

10,000 server * 1/6 hour = 1,666 hours = $166 - $15 = $151.

Someone less lazy than me could put this into a closed-form equation, with a confidence interval, rate and number of blocks specified, I'm sure.

I find this really interesting: right now someone could profitably offer a 'turbo' button for roughly double these numbers, so about $200 to $300 per 5-block generation. This would also not massively impact difficulty the next block cycle as it only ran briefly.

Thoughts or comments?



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August 11, 2010, 08:02:50 PM
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Think about this if someone wanted to screw with bitcoin... and had lots of money to waste Cheesy they could rent the 1000000 or whatever CPU cores. Burn through the 2016 blocks, and then take them offline. Difficulty would go sky high... and blocks would take hours or days to generate.

Once we finally got through the next 2016 blocks, the person could do it again.

But, that's if someone wanted to waste tons of money.

Is there a max adjustment? Or just a minimum difficulty?

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August 11, 2010, 09:06:48 PM
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Is there a max adjustment? Or just a minimum difficulty?
Adjustment is limited at 400% (up or down)

I was thinking today about the cost of speeding up the time to get, say 5 blocks generated if one was impatient for a purchase to be confirmed.

I find this really interesting: right now someone could profitably offer a 'turbo' button for roughly double these numbers, so about $200 to $300 per 5-block generation. This would also not massively impact difficulty the next block cycle as it only ran briefly.

Thoughts or comments?
Or you could just pay the seller the extra $300 to ship you the goods 'early'.

If they want to do that that is fine. I don't understand why you'd want to do it.
The system is pretty good at adjusting to in/out flow of computer power.


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August 11, 2010, 09:35:01 PM
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I too am unclear on the merit of "sped up confirmation".  The confirmations are intended to come at a steady and mostly-constant rate.

What does either the buyer or seller have to gain by spending real money to rush it?

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August 12, 2010, 03:11:34 PM
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Well, speed is always desirable for a purchaser and deliverer of X item, please refer to Escrow discussions here among others for some reference: being sure that the transfer is 'real' takes time, and for the two parties in a transaction, they almost always want that assurance immediately.

The hosting person could just as easily take BTC as dollars, so I don't think that's the point, really.

Regarding "Screwing with the network" Yes, it would be annoying for everyone to have to wait 40 minutes per block for 8 weeks if someone had burned through 2016 blocks quite quickly previously.

Since BTC aren't economically viable to generate on US server farms right now, this is likely just an 'attack' vector, not a 'money-making' vector, at least without the added payments for speeding things up.


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August 12, 2010, 06:49:15 PM
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I was thinking today about the cost of speeding up the time to get, say 5 blocks generated if one was impatient for a purchase to be confirmed.

...

Thoughts or comments?

Or they could both get mybitcoins.com accounts and make the transaction immediate for free!

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August 12, 2010, 08:21:58 PM
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If, you know, they trusted mybitcoins.com.

I'm the CEO of CoinLab (www.coinlab.com) and the Executive Director of the Bitcoin Foundation, I will identify if I'm speaking for myself or one of the organizations when I post from this account.
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