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Show HN: Hyperledger – Open Payments Protocol

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Re: Show HN: Hyperledger – Open Payments Protocol

#3

Post by PaulRobinson »

admax88q wrote: post #2

The FAQ dismisses 51% attack quite quickly, while casually mentioning that it's vulnerable to a 33% attack. What prevents an malicious actor from getting 34% of nodes, and then turning them all bad at the same moment?

The same thing stopping 34% of banks all going bad at the same moment: the number of banks

> bad nodes are automatically detected and expelled quickly

I'd be curious how the detection mechanism works

Re: Show HN: Hyperledger – Open Payments Protocol

#5

Post by feichtinger »

admax88q wrote: post #2

The FAQ dismisses 51% attack quite quickly, while casually mentioning that it's vulnerable to a 33% attack. What prevents an malicious actor from getting 34% of nodes, and then turning them all bad at the same moment?

Thanks for taking the time to read through!

The wording on that could be improved a little because there's a bit of a distinction between total computing power and number of nodes.

It's a proven result that in asynchronous systems with potentially malicious nodes, 1/3 is the maximum number of faulty replicas that can be tolerated. Here's a paper with a proof: http://zoo.cs.yale.edu/classes/cs426/2012/bib/bracha85asynch...

Bitcoin mixes things up a bit by also taking into account total computing power, but is still vulnerable to attacks where more than 33% of nodes are controlled, like selfish mining: http://hackingdistributed.com/2013/11/04/bitcoin-is-broken/

If more than 33% of nodes are compromised at the same time the good nodes will not accept bad transactions, they will simply wait until the consensus pool is fixed or removed and then continue normally.

Of course, with enough nodes it should be very unlikely for an attacker to get control of that many nodes at once.

Re: Show HN: Hyperledger – Open Payments Protocol

#7

Post by danoprey »

tonetheman wrote: post #4

Seriously I am too stupid to even know what this is... even after I read the FAQ. :(

Haha. Perhaps we need to update our intro then, as I highly doubt that's true! Essentially, hyperledger is a decentralised set of servers (owned and operated by lots of different people). Each server has the same collection of ledgers, accounts and balances, as each other, i.e., they have consensus over who owns what. When there is a transaction between accounts, the client that controls the account notifies one server, which then checks this is possible with all other servers. Each client and server sign every request they make, so fraudulent transactions can be detected easily and bad clients or servers can be blacklisted.

Re: Show HN: Hyperledger – Open Payments Protocol

#9

Post by feichtinger »

PaulRobinson wrote: post #3
admax88q wrote: post #2

The FAQ dismisses 51% attack quite quickly, while casually mentioning that it's vulnerable to a 33% attack. What prevents an malicious actor from getting 34% of nodes, and then turning them all bad at the same moment?

The same thing stopping 34% of banks all going bad at the same moment: the number of banks > bad nodes are automatically detected and expelled quickly I'd be curious how the detection mechanism works

Well, that would partly depend on the consensus pool as they may have their own blacklisting mechanisms, but broadly every message in the system is signed by the client making the request, and the consensus node passing it on. Every signature is published, so consensus nodes passing on messages that were incorrectly signed can be detected very easily. There are other attacks (not forwarding any messages is a simple one) that can be used, so pools will have to implement their own policies on timeouts/uptime etc.
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