Re: [Bitcoin-development] A mining pool at 46%
BTC Guild's response: 51% Mitigation Plan I want to start by thanking all users, new and old, for making BTC Guild become what it is today. I never expected a service that originally started on a mining PC in my dining room in April 2011 to go this far. However, recently BTC Guild has started to become too big. Users of Bitcoin are becoming scared that BTC Guild, either directly or through hacking/coercion, could be used to attack the network as it gets closer to 51% of the network. If this were to happen, it is likely many people would lose confidence in Bitcoin, as a single entity could control the network if it wanted to do so. I have put forward a proposal of my plans on how to mitigate this threat, but unfortunately nothing can be done without users taking some initiative as well. The following are the actions that will be taken if certain thresholds are crossed: More than 40% of the Network [last 2016 blocks] PPS fee will be raised from 5% to 7% on all new accounts. Old accounts will also be increased (PPS ONLY) to 7% after a difficulty change. If the pool eventually drops back under 40% for more than 72 hours, these fees will be turned back down to 5% after the next difficulty change. More than 45% of the Network [last 2016 blocks] Getwork based pools will be completely removed within 24 hours. All users on getwork have been warned in the past that it is a unsupported and not advised method of connecting. This should remove ~15% of BTC Guild's hash rate immediately. More than 40% of the Network again [last 2016 blocks] PPLNS fee will be raised from 3% to 4% after a 72 hour warning. This fee will be reduced back to 3% once the pool drops back under 40% for more than 72 hours. If you have questions or comments, please leave them on the forum thread related to this issue: https://bitcointalk.org/index.php?topic=168108.0 https://www.btcguild.com/index.php?page=home On 04/05/2013 07:12 AM, Peter Todd wrote: On Fri, Apr 05, 2013 at 12:13:23PM +0200, Melvin Carvalho wrote: Totally see the logic of this, and it makes sense. But I dont think the only risk is in terms of double spend, but rather 1) vandalize the block chain which may be difficult to unwind? Vandalize the chain how? By delibrately triggering bugs? (like the old OP_CHECKSIG abuse problem) Regardless of whether or not the vulnerability requires multiple blocks in a row, the underlying problem should be fixed. By putting illegal data into it? Fundementally we have no way to prevent people from doing that other than by making it expensive. An attacker having a lot of hashing power just means they can do so faster and a bit cheaper. -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Daryl Tucker da...@daryltucker.com -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
[Bitcoin-development] A mining pool at 46%
There was some chat on IRC about a mining pool reaching 46% http://blockchain.info/pools What's the risk of a 51% attack. I suggested that the pool itself is decentralized so you could not launch one On IRC people were saying that the pool owner gets to choose what goes in the block Surely with random non colliding nonces, it would be almost impossible to coordinate a 51% even by the owner Someone came back and said that creating random numbers on a GPU is hard. But what about just creating ONE random number and incrementing from there ... It would be great to know if this is a threat or a non issue -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] A mining pool at 46%
51% isn't a magic number - it's possible to do double spends against confirmed transactions before that. If Michael wanted to do so, with the current setup he could, and that's obviously rather different to how Satoshi envisioned mining working. However, you're somewhat right in the sense that it's a self-defeating attack. If the pool owner went bad, he could pull it off once, but the act of doing so would leave a permanent record and many of the people mining on his pool would leave. As he doesn't own the actual mining hardware, he then wouldn't be able to do it again. There are also other mining protocols that allow people to pool together, without p2pool and without the pool operator being able to centrally pick which transactions go into the block. However I'm not sure they're widely deployed at the moment. It'd be better if people didn't cluster around big mining pools, but I think p2pool still has a lot of problems dealing with FPGA/ASIC hardware and it hasn't been growing for a long time. On Fri, Apr 5, 2013 at 11:30 AM, Melvin Carvalho melvincarva...@gmail.comwrote: There was some chat on IRC about a mining pool reaching 46% http://blockchain.info/pools What's the risk of a 51% attack. I suggested that the pool itself is decentralized so you could not launch one On IRC people were saying that the pool owner gets to choose what goes in the block Surely with random non colliding nonces, it would be almost impossible to coordinate a 51% even by the owner Someone came back and said that creating random numbers on a GPU is hard. But what about just creating ONE random number and incrementing from there ... It would be great to know if this is a threat or a non issue -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] A mining pool at 46%
On Fri, Apr 5, 2013 at 2:30 AM, Melvin Carvalho melvincarva...@gmail.com wrote: There was some chat on IRC about a mining pool reaching 46% http://blockchain.info/pools The estimates on there may be a bit lossy. What's the risk of a 51% attack. The whole fixation on 51 as a magic number is a bit confused— I'll say more below. I suggested that the pool itself is decentralized so you could not launch one None of the pools listed there are meaningfully decentralized— before Luke whines, in theory the ones supporting GBT could be if used in a way that no one actually uses them. P2Pool is decentralized based on the same technology as Bitcoin itself, but it's certainly not as point and click easy as a centralized pool. On IRC people were saying that the pool owner gets to choose what goes in the block That is correct. Though I'd point out— the major pool ops all seem to be great folks who care about the future of Bitcoin— and the continued success of their very profitable businesses: a 50% mining pool with a 3% fee rakes in 54 BTC per _day_. The more likely threat isn't that pool owners do something bad: It's that their stuff gets hacked (again) or that they're subjected to coercion. ... and the attacker either wants to watch the (Bitcoin) world burn, or after raiding the pool wallet can't exploit it further except via blockchain attacks. Surely with random non colliding nonces, it would be almost impossible to coordinate a 51% even by the owner That makes no sense. A centralized pool is the miner, the remote workers are just doing whatever computation it tells them to do. Certainly these remote workers might switch to another pool if they knew something bad was happening... but evidence suggests that this takes days even when the pool is overtly losing money. Miners have freely dumped all their hashpower on questionable parties (like the infamous pirate40) with nary a question as to what it would be used for when they were paid a premium for doing so. It seems even those with large hardware investments are not aware of or thinking carefully about the risks. It would be great to know if this is a threat or a non issue It's important to know exactly what kind of threat you're talking about— someone with a large amount of hash-power can replace confirmed blocks with an alternative chain that contains different transactions. This allows them to effectively reverse and respend their own transactions— clawing back funds that perhaps had already triggered irreversible actions. This doesn't require some magic 51%— its just that when a miner has 50% the attack would always be successful if they kept it up long enough (long enough might be years if you're talking really close to 50% and he gets unlucky). Likewise, someone with a sustained supermajority could deny all other blocks— but that attack's damage stops when they lose the supermajority or go away. More interesting is this: An attacker with only 40% of the hashpower can reverse six confirmations with a success rate of ~50%. There is source for computing this at the end of the Bitcoin paper. I did a quick and really lame conversion of his code JS so you can play with it in a browser: https://people.xiph.org/~greg/attack_success.html -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] A mining pool at 46%
On Fri, Apr 5, 2013 at 2:48 AM, Mike Hearn m...@plan99.net wrote: but I think p2pool still has a lot of problems dealing with FPGA/ASIC hardware and it hasn't been growing for a long time. As an aside and a clarification— P2pool works great with FPGAs, and one of the largest FPGA farms I've heard of uses it. But it doesn't work well the old BFL FPGA miners— because they have insane latency. Likewise it doesn't currently work well with Avalon, again because of insane latency. P2pool uses a 10 second sharechain in order to give miners low variance but that means that if you have a several second miner you'll end up subsidizing all the faster p2pool users somewhat. It was basically stable with the network until ASICminer came online mining on BTCguild mostly and the first avalons started to ship, and then the network went up 10TH in a couple weeks (and now 15TH) while P2Pool stayed mostly constant. ForrestV (the author and maintainer of the P2pool software) would love to work on making Avalon and other higher latency devices first class supported on P2Pool, but he doesn't have one— and frankly, all the people who have them aren't super eager to fuss around with a 5BTC/day revenue stream, especially since the avalon firmware (and its internal copy of cgminer) itself has a bunch of quirks and bugs that are still getting worked out... and I do believe that p2pool helps reduce concerns around mining pool centralization. ... but I think as a community we don't always do a great job at supporting people who work on infrastructure— even just making sure to get them what they need to keep giving us free stuff—, we just assume they're super rich Bitcoin old hands, but that often isn't true. -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] A mining pool at 46%
On Fri, 5 Apr 2013 11:48:51 +0200, Mike Hearn wrote: However, youre somewhat right in the sense that its a self-defeating attack. If the pool owner went bad, he could pull it off once, but the act of doing so would leave a permanent record and many of the people mining on his pool would leave. As he doesnt own the actual mining hardware, he then wouldnt be able to do it again. Unless all the miners are monitoring the work they do for their pools and the actual miners that found the blocks noticed (unlikely) - the only way anyone knows which pool did anything is the source IP that first disseminates the new block. Also since it's unlikely that both of the doublespend blocks would be found by the same end miner, neither of them would know that the pool operator was responsible even if they were monitoring their work. There's nothing stopping the pool owner from channeling the doublespend blocks through some other previously unknown IP, so I don't think they would suffer any reputational damage from doing this repeatidly. Robert -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] A mining pool at 46%
On Fri, Apr 05, 2013 at 12:13:23PM +0200, Melvin Carvalho wrote: Totally see the logic of this, and it makes sense. But I dont think the only risk is in terms of double spend, but rather 1) vandalize the block chain which may be difficult to unwind? Vandalize the chain how? By delibrately triggering bugs? (like the old OP_CHECKSIG abuse problem) Regardless of whether or not the vulnerability requires multiple blocks in a row, the underlying problem should be fixed. By putting illegal data into it? Fundementally we have no way to prevent people from doing that other than by making it expensive. An attacker having a lot of hashing power just means they can do so faster and a bit cheaper. -- 'peter'[:-1]@petertodd.org signature.asc Description: Digital signature -- Minimize network downtime and maximize team effectiveness. Reduce network management and security costs.Learn how to hire the most talented Cisco Certified professionals. Visit the Employer Resources Portal http://www.cisco.com/web/learning/employer_resources/index.html___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
