Bitcoin Forum

Would some enlightened individuals please explain how having more hashing power than 51% will affect an attack?

Will the speed with which they can rewrite blocks increase?
Will having 50.001% effectively be the same as having 60%?
Could a 45% attack work if the attacker gets lucky by finding the correct hash before the other 55%?

don't forget that nothing can be rewritten with this type of attack prior to block 140,700 as that is the last checkpoint.  this will be moved up soon.

the more power you have, the more blocks in a row you can get. if you want to continually degrade the network, at least >50% is required.

many people focus on the double spending aspect of re-writing history, but the reality is that there will probably never be a big enough incentive to spend the money to make double spends. anyone who is going to spend the money to get >50% is going to attempt to take down the network, and all that is ever required is just greater than 50%. they can always re-write history, eventually, at that point. locking in blocks with each software release is just a very small band-aid and does not really do anything effective since trying to re-write "ancient" history is pointless when they can just make sure no new transactions ever confirm, or any that do will eventually be reversed.

Why would anyone spend time and money interfering with confirmations?

um I did say why in the post. to take down the network. if bitcoin starts becoming a real threat to the established financial institution, it would be pocket change to them and by far in their best interest

pocket change?  how so?  the network is multiples in terms of hashing power of the largest supercomputer on earth.  how much does one of those supercomputers cost?

Yes, higher hashrate means the attacker can close the gap faster. With 51% or 50.001% he is guaranteed to outpace the network from any disadvantage (say 6 blocks), eventually. The guarantee doesn't tell you how long it will take, and in fact with 50.001% it would take on average about 6 years (it's random so it could be much less). With 51% it's 2 days. (These estimates are with a very simplified model, actual numbers could be different).

Yes, he has a chance of success but no guarantee.

you have 3,500 posts on this board and run some financial site. your "feign stupid" shtick is getting old.

A simplified model gives a result of 5 hours, but finding a more accurate estimate requires some work.

hey, i'm just asking you to define pocket change.

your title really should be changed from Hero Member to Bitcoin Information Minister.

I estimate it would take about $30 million USD to reliably take down the bitcoin right now.

how do u arrive at that number?

About $1500 per GHash multiplied by 15000 max current network hash rate (with some overhead) =$22.5 million
leaving $7.5 million for administrative and electricity costs.

This is just very quick estimate, obvious corrections welcomed.

really, we're going to take a gross exaggeration so out of context as to call it "ridiculous"? even though it has surely been used in the same manner many times before. am I writing for an esteemed publication or on a fucking message board?

besides, comparing the bitcoin network in integer operations when supercomputers are measured in floating point operations is well-known around here to be a misguided comparison and only goes to show that cypherdoc is, once again, trying to be deceptive to people asking legitimate questions in what I can only see as being a shill for his own personal gain. he may not like my opinion or my exaggeration, but that is not course for conflation with obvious intent to confuse and derail

i disagree with this logic.  if the US gov't or some financial institution were to enter the market for gpu's the cost of those gpu's would skyrocket pushing the cost into the billions i'd estimate.

look at the Butterfly Lab Rig unit.  b/c of the expressed interest the price has gone from $24,890 to $29,890 and they haven't even produced one!

trying to be deceptive?  i just asked you to explain your claim of "pocket change".  you are one sensitive dude.

shill for personal gain?  i am just one of many who have a vested interest in Bitcoin around here.

how about you and Encoin?  just who has a vested interest?  how's that going btw?

confuse and derail?  you have problems.

no we don't.  Etlase has conflicts with many ppl around here.  i'm just the latest.

Cypherdoc, get a clue or gtfo. https://bitcointalk.org/index.php?topic=52166.msg623111#msg623111

If an entity decided to spend $30M to attack or take control of Bitcoin, they would NOT got out to buy GPUs in retail stores.
They could design a 65nm ASIC for a couple of millions $ of NRE and then produce a ton of them probably for less than 100$ per GH/s (wild guess based on 45nm FPGA based systems going for close to $1 per MH/s  in single quantities today. A dedicated, mass produced ASIC design should be able to be 10 times more cost efficient than a retail FPGA design).
Heck, if anyone wants to give me $5M, I'm willing to give it a shot.  8)

Why you think that almost unlimited supply can take down Bitcoin? Why there is chronic shortage of High-End Radeon cards? Sure, banks can create money from thin air, but they cannot create GPU chips in the same way. Not counting all components needed to assemble functioning GPU card. To take down Bitcoin there is need for "Bombe" style machine that cracked german Enigma. Think about innovation and dedication required to do something similar today. Think about creating a building full of malicios Bitcoin ASICs.

The point is, if you are going to invest in bitcoins, also invest hashing power.

are you blind?  we are over 3yr into this and 1 Bitcoin is worth 5 USD.  there are alot of ppl who apparently disagree with you.  i'm waiting.

Disagree with what ?  Face-palm is all I meant.

You had no clue about the USD value of Bitcoin security.
I think you also had no idea of the IT budget of banks, yet you seems to be willing to provide financial advices.

Your not thinking about ASIC's if they want to take down the network they could just pay like 5-10 million to have ASIC's made and easily have enough hashing power to take down the network.

and yes 5-10 million is pocket change to them

Its a good advice but when you buy you are also indirectly supporting the miners, so they can increase their hardware.

I think that if the main client got support for easy P2pool mining lots of people would mine somewhat just to support the network.

Atleast I would, but I do not have the time to put effort into buying a mining rig.

i fail to see how you could conclude this.  nothing i said would indicate that.  plus this topic has been discussed up and down the forums for years now and there is plenty of disagreement.  also that calculation is highly dubious and is based on a simple calculation of hardware based on today's prices which is unreasonable.  any big player entering a market for say asic components or whatever of this magnitude would shove prices thru the roof.

i gave you an small example of the Butterfly Rig.  that price has moved up 20% just from the limited demand of a few small Bitcoiners that you apparently think are making a mistake investing in such a high price machine as well.

this is just a plain and simple ad hominem attack.  you seem to just be repeating Etlase's.  do you have any creative concrete criticisms of your own?  

and what does my blog have to do with the discussion at hand?  you make an assumption and then create a diversion.  try to advance some ideas that pertain to this thread.

and as to regards to the number of my posts you referred to in the pm you just sent me, what if i say "b/c you have so few posts you can't possibly know anything about Bitcoin"?

is this the entity you guys are talking about smashing the network?:  http://www.wired.com/threatlevel/2012/02/forgotten-password/

no point in any kind of logical discussion here, move along

actually, i agree with you on the move along part.  as i said, this topic has been discussed repeatedly in numerous threads and there is plenty of disagreement with well thought out arguments on both sides.  its useless hashing this out here yet again.

i don't have the specific numbers or ability to work it out, but i know its a laughable idea that a powerful entity with the intent of dominating the compute power of the network would hit up newegg for gpu's.

the absolute closest this entity would come to buying off the shelf would be to get the most powerful 22nm FPGA chips on the market today, and fab their own boards.

most likely though, as mentioned they'd just build their own custom ASIC solution.

those pointing to the current hash rate of existing super computers are also missing the mark.  those configurations are not optimized for efficient hashing.  the same money (cost to originally acquire adjusted for inflation) a top level super computer cost, invested in a custom system designed specifically for hashing, would dominate beyond 51%.

You are right in saying that it would be pocket change in terms of the financial power of the stakeholders.
However financial institutions tend to be extremely risk averse.
For a budget in the millions, the approval process is not a breeze: what banks's CEO will engage first? Who will be responsible for the risk analysis ? (litigations ?)
If it's a government agency, what is the mandate and charter ? Is it not like opening a can of worms ? Will it not backfire ?
Then again the best interest of a bank could very well be to adopt the technology instead of trying to make as if it was never invented.

Remember, this never needs to go public. If bitcoin gets taken down, we will only know that it happened, not who did it or why. Even if it is later discovered who did it, the damage is still done. If people lose millions of dollars and the Big Problem of the bitcoin protocol is exposed, I don't really see how it will backfire. All of a sudden now the general public is going to run away from big banks and government aid? Not likely.


Highly unlikely. The Rothschild era of bitcoin has come and gone and the players are already decided with little chance of big banks making much headway. They are not going to relinquish control of money to the early adopters.

but yet you were willing to try and start an alt chain by the name of Encoin which apparently has failed since i don't see it in your sig anymore.

if it had been successful then YOU would have clearly been an early adopter and stood to gain the most from its success.  i guess in that scenario an alternative form of money would be OK, right?

but since you're clearly not a Bitcoin early adopter, it must be a bad thing and is highly likely to be destroyed by these big entities?  stop with the FUD.