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It's unclear to me specifically what type of attack you are describing. One does not "simply take over majority control of the network". Edit: Looking at the

It's unclear to me specifically what type of attack you are describing. One does not "simply take over majority control of the network". Edit: Looking at the votes, it seems like I may be the only one who it's unclear to. Could someone please fill me in?

kayamon 4y ago
There is only one valid blockchain at any given time -- the longest one (currently Bitcoin). Any attempt such as this one to create a new blockchain will always be shorter than the pre-existing longer blockchain, thereby making this attempt susceptible to a 51% attack from outside its network.
- everfree 4y ago
  Bitcoin is not the only valid blockchain in existence, if that's what you're implying (your comment is unclear to me). A blockchain's length (or more specifically, total accumulated work), does not play a direct part in determining its susceptibility to 51% attacks. Furthermore, blockchains are only susceptible to cross-chain attacks like this when they use a proof of work consensus mechanism and also share the same hashing algorithm.
- throwawaymaths 4y ago
  For some definition of "valid". Nobody is stopping you from trusting a different "parallel universe" branch of the Blockchain, you just don't do it because most likely no one else will trust your work and it will be pointless work. Or you do in fact do it because it's a coordinated soft fork (there is a subpopulation that you care about that will together accept this parallel history and reject the mainline history). Construct an appropriate analogy for the bgp use case.
- dgellow 4y ago
  If you fork, don’t you have the same length (at least at the moment of fork), by definition?
  - kayamon 4y ago
    You fork a blockchain by linking new blocks on the end (with bitcoin.pdf forming an implicit start node they all kicked off from). Whichever of the forks persuades enough people to continue mining on it becomes the real blockchain and the people will slowly stop working on the other forks. The shorter blockchain will never find enough people to mine it when there's a larger more lucrative blockchain to mine.
    - FabHK 4y ago
      Except that it has happened multiple times.
ixfo 4y ago
The internet basically only works because small entities have as much standing and control as large entities. This is also why things like RPKI are required, to prevent small (and large!) actors causing disruption through malicious or accidental configuration of e.g. BGP. Whereas in a blockchain, if you assume the participants are the same set of actors - which would make sense - then it would be very easy for a majority of network control to be held by a Google, an AT&T, a China Telecom, etc. Introducing third-parties who are not neccesarily involved in the operation of networks to said blockchain also opens up BGP operators to a whole new raft of attacks. Want to blackhole an ASN? If you can convince a smart contract that the routing policy for that ASN is "drop all traffic" then you don't even need to compromise people's routers or muck around with all that messy DDoS stuff. Bad, bad idea. Just like 99% of stuff with the word "blockchain" in it.
- dgellow 4y ago
  What would you say are the 1% of stuff with blockchain in the name that aren’t bad ideas?
  - rvz 4y ago
    Don’t bother asking here about anything with the word ‘blockchain’ since not only it is poisonous here, but it is guaranteed to be quickly dismissed without any curiosity of the 1% of applications it may have. Here are a few that are part of that 1%: [0] https://skiff.org https://skiff.org [1] https://ens.domains https://ens.domains [2] https://impervious.com/beacon https://impervious.com/beacon
    - throwaway82652 4y ago
      I'm sorry but absolutely none of those applications need blockchains or even benefit from them at all. If you want to discuss this I could go into extreme detail why that's the case. I can understand being excited about the promises made by them but at some point we all need a good reality check. Having curiosity doesn't suggest any particular kind of acceptance, we can actually accept that something is universally useless and not worth our time. I'm not saying this because I want to crap on people's startups, I'm saying this because they could make a lot better products if they weren't getting wrapped up in this.

kayamon 4y ago

There is only one valid blockchain at any given time -- the longest one (currently Bitcoin). Any attempt such as this one to create a new blockchain will always be shorter than the pre-existing longer blockchain, thereby making this attempt susceptible to a 51% attack from outside its network.

everfree 4y ago
Bitcoin is not the only valid blockchain in existence, if that's what you're implying (your comment is unclear to me). A blockchain's length (or more specifically, total accumulated work), does not play a direct part in determining its susceptibility to 51% attacks. Furthermore, blockchains are only susceptible to cross-chain attacks like this when they use a proof of work consensus mechanism and also share the same hashing algorithm.
throwawaymaths 4y ago
For some definition of "valid". Nobody is stopping you from trusting a different "parallel universe" branch of the Blockchain, you just don't do it because most likely no one else will trust your work and it will be pointless work. Or you do in fact do it because it's a coordinated soft fork (there is a subpopulation that you care about that will together accept this parallel history and reject the mainline history). Construct an appropriate analogy for the bgp use case.
dgellow 4y ago
If you fork, don’t you have the same length (at least at the moment of fork), by definition?
- kayamon 4y ago
  You fork a blockchain by linking new blocks on the end (with bitcoin.pdf forming an implicit start node they all kicked off from). Whichever of the forks persuades enough people to continue mining on it becomes the real blockchain and the people will slowly stop working on the other forks. The shorter blockchain will never find enough people to mine it when there's a larger more lucrative blockchain to mine.
  - FabHK 4y ago
    Except that it has happened multiple times.

ixfo 4y ago

The internet basically only works because small entities have as much standing and control as large entities. This is also why things like RPKI are required, to prevent small (and large!) actors causing disruption through malicious or accidental configuration of e.g. BGP. Whereas in a blockchain, if you assume the participants are the same set of actors - which would make sense - then it would be very easy for a majority of network control to be held by a Google, an AT&T, a China Telecom, etc. Introducing third-parties who are not neccesarily involved in the operation of networks to said blockchain also opens up BGP operators to a whole new raft of attacks. Want to blackhole an ASN? If you can convince a smart contract that the routing policy for that ASN is "drop all traffic" then you don't even need to compromise people's routers or muck around with all that messy DDoS stuff. Bad, bad idea. Just like 99% of stuff with the word "blockchain" in it.

dgellow 4y ago
What would you say are the 1% of stuff with blockchain in the name that aren’t bad ideas?
- rvz 4y ago
  Don’t bother asking here about anything with the word ‘blockchain’ since not only it is poisonous here, but it is guaranteed to be quickly dismissed without any curiosity of the 1% of applications it may have. Here are a few that are part of that 1%: [0] https://skiff.org https://skiff.org [1] https://ens.domains https://ens.domains [2] https://impervious.com/beacon https://impervious.com/beacon
  - throwaway82652 4y ago
    I'm sorry but absolutely none of those applications need blockchains or even benefit from them at all. If you want to discuss this I could go into extreme detail why that's the case. I can understand being excited about the promises made by them but at some point we all need a good reality check. Having curiosity doesn't suggest any particular kind of acceptance, we can actually accept that something is universally useless and not worth our time. I'm not saying this because I want to crap on people's startups, I'm saying this because they could make a lot better products if they weren't getting wrapped up in this.