Possible attack scenario

Kimba

Stellar is said to be secure due to its consensus protocol. Unlike classical coins, an attacker cannot launch a 51% attack by obtaining a majority of the hash power. What if an attacker would spontaneously create, say, 3 times the amount of nodes that currently exist in the stellar network? They would, of course, all trust each other, and distrust the existing nodes, and thus mutually claim to form the correct consensus and previous nodes to be a malicious offspring. Is there any protection against this, is it a possible attack scenario?

Thanks

CryptoMediaNetwork

Im guessing that the more the network grows and new nodes are connected, the less and less chance there will be for this to happen. Almost impossible. Each node holds the whole history of the network and takes weeks to download the info so in order to have over 50% of nodes on the network would be a hell of a job for someone. Also before all the new hacker nodes where live, someone would be asking questions to who owns them.

Kimba

Okay, that is a valid argument, but it goes no further than Bitcoins argument about its giant amount of hash power. If I were to attack Stellar, I could theoretically download the network to 1000 servers (or maybe even a big server with 1000 IPs? Like Googles virtual servers) and start all nodes at the same time. This is the same as what happens when you want to attack a POW Currency, with the small difference that attacking a POW Currency costs you lots of $ every hour of the attack, while attacking Stellar or Ripple merely costs buying/renting a couple of servers. And several POW Currencies have been attacked this way this year already. Am I missing something?

Unsinkamoto

I am not a technical security expert but here is my understanding.

It would not matter how many untrusted nodes you launched. They could only affect consensus for the quorum slices they are apart of, which do not include any trusted slices.

They could not override the trusted network.

The closest equivalent to a 51% attack would be if those nefarious nodes managed to become 66% of the trusted nodes in a trusted quorum slice. Then they could falsify transactions within that slice, but the other slices would reject those transactions.

I believe this would freeze the Stellar network until it was resolved to prevent a hardfork. Possibly only for the affected slices?

CryptoMediaNetwork

You have a valid point and i appreciate you bringing it up. There are people much more knowledgeable than me on the subject but i try!

For a better answer you will be better off asking here http://slack.stellar.org/ and here https://galactictalk.org where the devs hang out.

I think that the network will grow so fast that it will be impossible to have over 50% of the nodes, at the moment there are few so it could be a problem, though nearly all the nodes are owned by IBM and a few partners

jamie

@"Kimba"#7457 A similar question was asked on Stellar's stack exchange which might help :

https://stellar.stackexchange.com/questions/160/how-does-the-stellar-consensus-protocol-prevent-sybil-attacks

Kimba

Thanks, that explains it! Hence Stellar should be pretty secure.

It does make me wonder how nodes decide on who to trust though. If every new node simply trusts well known nodes (such as those by IBM) and cannot figure out on his own who to trust next, then there will be few mighty ("autoritarian") nodes and many less worthy ones. For example, if I make my own node on this computer, who should ever care to trust me? Would I even contribute to the trust network, if nobody selects me as a trustworthy member and only I trust others?

Thanks for answering this new question :P

Unsinkamoto

Well node operators choose which nodes to trust. If they wanted to they could make their own private slice of nodes, couldn't they?

Every independent node operator that does not trust the core SDF-associated nodes has the potential to create a collusion-resistant network of "independent" slices. Browncoats. Shiny.

Itsame

I assume there's some protection built in if a group of private nodes get set up and all trust each other. The rest of the network wouldn't trust them so they couldn't do damage surely?

Unsinkamoto

Correct, they could do no damage to the rest of the network.