Every day we discover new advantages of decentralized systems and peer-to-peer networks . Well designed P2P systems, provide greater resilience against attacks and accidental disruptions. Nevertheless decentralization comes with a price: consensus must be reached by voting or by proof-of-work, and both solutions tend to be slower than traditional centralized decisions. Instant payments requires instant consensus, and that’s something that is difficult to achieve. Two posts ago I proposed a fully decentralized solution that achieves confirmations in around 15-25 seconds. Can we do better? Probably, but that would require a great investment to inter-connect the whole world by fiber optic. Currently the packet delay is influenced by the length of the route and the interaction between the TCP reliability and congestion control protocols. Other important factors are application level manipulation of the data, propagation delay, serialization, data protocols, routing and switching, queuing, buffing, bandwidth and noise. Can we do better with the current Internet infrastructure? I think we can, by designing systems that behave like centralized ones, but can disperse into fully distributed ones if something goes wrong. Nature has many examples of colonies that have a queen, but if the queen dies somehow manage to re-elect a new queen that all obey. This is what the MinCen protocol tries to do: it chooses a master node that decides which is the next block when there are competing chains. Everyone then follows this decision. But if the master node tries to cheat then every miner starts looking for another master node, in such a way that individual decisions converge to a new global selection. Are you designing a new cryptocoin? give a try to the MinCen protocol (preliminary version of the paper available here).
MinCen: A new protocol to achieve instant payments
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#1 by Tothe on March 20, 2014 - 11:05 pm
Could a payment processor implement this idea for the current Bitcoin network, how would it work ? trusting mining pools ? How do you define ” try to cheat” ?
#2 by SDLerner on March 21, 2014 - 2:52 pm
I could: miners should broadcasts a partially-solved blocks, they should also add in the coinbase field information regarding who the master is. But since Bitcoin block interval is 10 minutes, there is no big benefit to reduce the stale block rate: payments will still require at least 10 minutes to confirm.
#3 by Ray on March 29, 2014 - 4:54 am
I worry here that an attacker with resources could fairly easily become ‘manager’ on demand, simply by throwing hardware at having good connectivity and publishing shares that point to the desired manager node. After that, one could create a disruption throwing the network into a few minutes of chaos at a time precisely selected to interfere with someone’s payment or protocol.
#4 by SDLerner on March 31, 2014 - 4:29 pm
But “chaos” is not the correct word. Since users can sense the network state (because of the passing shares and ACKs), they can detect any attempt of disruption and prevent erroneous information to be passed to the users. So all the “chaos” ends-up being a little more delay in the confirmation times. And afterwards the attacker has lost the master position, lost the master reward, lost the reputation, and gained almost nothing.
#5 by Jack on April 1, 2014 - 10:33 am
This is based upon an entirely false premise. An ant queen is not elected, nor does she give orders. The queen merely produces eggs – nothing more. Organisation in an ant colony is an emergent consequence of the discrete actions of all the ants.
A single point of failure such as proposed by mincen would be desperately problematic and runs directly contrary to the benefits of a decentralised system as it seems to value, for the purpose of expediency, a hierarchical representative democracy of sorts.
#6 by SDLerner on April 1, 2014 - 12:49 pm
I never talked about ants. In fact, the nature analogy is just for inspiration, and nothing else. The protocol works because the right incentives are in place, from the game theoretic point of view. The master has no incentive to cheat, and the miners have an incentive to choose a master. Is pure mathematics, and I see no ants.
#7 by Jack on April 1, 2014 - 9:50 pm
Er… “Nature has many examples of colonies that have a queen, but if the queen dies somehow manage to re-elect a new queen that all obey.”
Anyway – I know, I’m just being a pedant. 😉