How to prove that you are participating in an activity?

[mczarnek]

So, I'm playing around with an idea that involves a decentralized system and a number of nodes agreeing on something.  Maybe someone here can help.

Let's say I want this to be really secure, so I randomly pick 30 nodes, via a proof of work like system, I send those 30 each a small packet, they process it and return it. Say that out of those 30, at least 28 are required to reply.

If they reply then there is no problem, I can deal with malicious replies.  The one thing I can't figure out is how can you quickly deal with them simply deciding not to reply?  I'm thinking that maybe I can find a way to let them prove they have replied by propagating their own message to the network, and those that don't reply get kicked off. It's not important if it's a double spend or anything like that, they can either reply with a yes or no, if both are detected, then they are cheating.

I would like to be able to kick them out, or black list their ip address for a day or something like that.  The issue is that I have to be able to prove to the entire network that they are haven't responded within a minute or two.

Any thoughts?

[kuverty]

Well, you can of course prove that you have got a reply, if it is signed. But there can't really be a way that you can prove that you have not gotten a reply; who knows, maybe a reply was sent but you somehow did not get it. Like trying to prove you did not hear someone shouting, maybe you did, maybe not.

I think you are on the right track, you must have the nodes broadcast their message through the rest of the network somehow, maybe let the nodes relay each others' messages. I don't know your application so it's hard to say any better.