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Author Topic: Selfish mining  (Read 2955 times)
afbitcoins
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November 05, 2013, 11:50:48 PM
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Research by the Department of Computer Science, Cornell University suggests bitcoin is vulnerable to selfish miners gaining more than their fair share of the spoils of mining.

Allegedly a selfish group will quickly become a majority as individual miners seek to join that cheating group to reap the higher rewards, like a snowball growing bigger as it rolls down the mountain. This group will then become the controllers of bitcoin and it will become effectively centralised and controlled by that group of miners rather than the decentralised currency we all value.

heres is a link to the research paper if you are interested, http://arxiv.org/pdf/1311.0243v2.pdf

It is claimed by the same researchers that they can also implement a modification to bitcoins to help resolve the problem. I think this would be a huge mistake and I’ll explain why.

First such pools with greater than 25% share of mining already exist. http://blockchain.info/pools
Therefore if the patch was implemented now it would mean instead of anyone being able to cheat only those big pools could cheat.

The proposed patch takes that away freedom to choose to cheat replacing it with a crippled network in which small guys can’t cheat, but the big guys can. In other words it is the software patch that guarantees the snowball effect, not the strategy of selfish mining.

I'm hoping to stimulate some interesting debate here about the problem, and the proposed patch and hopefully spread awareness about the danger of the patch and why it would be suicide to implement it.

Thanks

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full article on my blog http://afbitcoins.wordpress.com/2013/11/05/selfish-mining-possibilities-discovered/
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November 06, 2013, 12:46:48 AM
 #2

Each regulation does more harm than good in the long term. So the quiestion is, what they want in it that they want to regulate? Or are they just usefull idiots?

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November 06, 2013, 02:35:42 AM
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Here are my thoughts from another thread after reading the paper:
I just read it.  They misunderstand one key thing:
Quote
Currently, when there are two branches of equal length, the choice of each miner is arbitrary, effectively determined by the network topology and latency. Our change explicitly randomizes this arbitrary choice, and therefore does not introduce new vulnerabilities.

The choice is not arbitrary.  Miners work on the first block they see.

The "attack" is to withold a found block until someone else publishes a block.  Then you publish your block and split the miners.  Except, you didn't broadcast until you saw the other block.  And by that time, probably half of the network had seen it too.  So that leaves you, a single broadcast node competing against the broadcast power of half the nodes in the network for the remaining portion the mining power.

Their "fix" is to randomize the choice any time a node sees a different fork than the one they see.  Not only does this require you to track each fork (so they don't spam you with the same one, eventually you would "randomly" choose it), but it allows their attack a chance to work.  Without their proposed fix, they would be pissing into the wind.

https://www.bitcoin.org/bitcoin.pdf
While no idea is perfect, some ideas are useful.
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November 06, 2013, 04:51:33 AM
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i don't know about bitcoin but this have already happend one time for litecoin, anyone remember notroll.in :v
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November 06, 2013, 09:44:46 AM
 #5

and who cares if BTC guild is 51%... BTC guild still consists of thousands of different miners. People who want to change something in Bitcoin probably do not want to for the best for bitcoin

afbitcoins
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November 06, 2013, 04:19:17 PM
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When I first came across this research paper i was slightly alarmed, worrying that the bitcoin programmers might be hoodwinked into making the modifications that were proposed.  but after seeing other reactions of bitcoiners on this thread and elsewhere don't think i needed to worry so much about this threat. People seem very wise to this kind of tampering. Great community.
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November 12, 2013, 09:46:29 PM
 #7

This "selfish mining attack" is based on withholding a mined block and only publishing it at a later point in time, right?

Being aware of the fact that each block contains a UTC time stamp, here's my defense proposal against this attack:

Why shouldn't the miners simply make a tiny adjustment of their acceptance criterion for new blocks received from other miners? This would avoid the whole attack scenario from the start.

In detail the solution would look like this:
Each miner that considers itself "well connected" to the network (i.e. not in the initialization state) will NOT accept a new block if its timestamp upon arrival is older than
 t_receive_time - t_delta,
where t_delta is hard-coded in the miner software as e.g. [30 seconds] (see e.g. here).

Every honest miner will publish its block immediately, so it should propagate to almost all other bitcoin miners within less than [30 sec].

A selfish miner, acc. to this attack scenario, who withholds its block for some duration, will get its block rejected by the honest majority.

A further amendment could be:
If
 t_timestamp < t_receive_time - t_delta,
then a miner will first reject the new block, but if it has not received any newer block after t_confidence, where
 t_confidence = (t_receive_time - t_delta) - t_timestamp,
then it will accept it anyway.


PS: Side note: This defense mechanism against selfish mining only works properly if
 avg. block propagation time << t_delta [30 sec] << block generation interval [10 min]
This is just another reason why feathercoin or litecoin with their "unhealthy" short confirmation times are not eligible for this defense strategy. Satoshi had a good reason for choosing a confirmation time well above the block propagation time.

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October 03, 2014, 06:10:15 PM
 #8

What if all the miners adopted a selfish mining algorithm?  Wouldn't that eliminate any advantage?  Maybe if you tweaked the parameters or the algorithm you might gain a slight advantage but then everybody starts tweaking.

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October 06, 2014, 04:57:39 PM
 #9

bitcoin mining is inseparable from the meaning of the bitcoin currency itself is freedom without any interference from the world bank or the government, the existence of uniform distribution of the bitcoin that exist throughout the world, is a reflection that there is no buildup of bitcoin is only on one side only, it is proving that ownership is not selfish ownership bitcoin currency current ...  Roll Eyes
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