Someone over on Reddit posted a patch to Luke's latest BFGminer which provides a command line option to turn on block withholding attacks.
The post is in the "I'm selfish mining at ghashio" thread. Here's the link they posted for convenience:
http://pastebin.com/d1ptqDFvI can think of several incentives to use such an attack:
- To prevent a pool like GHash from cornering the mining market (and thus causing prices to fall) by negatively impacting their luck. This should providing incentive for miners to switch to another pool
- To attack pools other than one's own in order to entice their users to come to your own pool
The second incentive seems like it would only work for individuals/groups in direct control of a large amount of hashing power -- such as GHash/CEX.
Perhaps this will turn out to be just the sort of tool the Bitcoin community needs to keep mining pools from gaining too much market share? Or perhaps it will usher in a new stage of mining wars. Either way, it seems like it has the potential to alter the balance of power by giving the mining community some power to punish misbehaving pools.
This is a horrible precedent to set.
In your 1st example the users of ghash have nothing to do with how much hashpower ghash has as a pool. They are the ones that will be affected. Since ghash does not charge miners a fee they will not be affected by selfish mining.
Selfish mining in general will, in the long run decrease security in the Bitcoin network. It will cause miners to distrust pools and solo mine. The problem with solo mining is that most smaller miners do not have enough hashpower to solo mine effectively (their profits would be based too much on luck) and would stop mining. This would both further centralize the network and weaken the network.
As it stands now, miners can easily leave a pool they do not like for whatever reason.
