Bitcoin Forum

Would BTC protocol survive with 3 or four nodes only?

Depends who was running those nodes, the protocol can survive on more than 1 node. But would you trust only 3 people to run those nodes? Probably not.

When there are too few nodes bitcoin becomes susceptible to a low level network attack.

Right. But then, with 3 nodes, there would be only 3 confirmations for a transaction, correct?

Ok. And that depends on the number of miners among the 3 nodes, or it wouldn't matter?

No. A block is a confirmation, not a node. A transaction does not have a set number of confirmations, in fact they'll go on adding "confirmations" forever.

But if you don't have enough nodes than those left can manipulate easily. Transactions could easily be blocked, and even reversed if conditions are perfect. Confirmations would be worth less on a chain with only three active nodes, compared to say one confirmation on a chain with thousands of nodes.

A node is not a miner, but a miner has to be connected through a node. The node decides which transactions are included in the blocks the miner attached to the node is trying to solve. Only one miner per node AFAIK. Pools are different, they act as one miner.

 

No, attacker just needs to be able to create enough attack nodes to disrupt the rest of the network.

No, the attacker not only has to come up with attack nodes but has to match or best the hashing power of the legitimate nodes still on the network. Until that point the most they can do is delay transactions, and waste their own money making invalid blocks...

 

Yes, I know. This attack is about gaining control of the network, not the blockchain.

 I see. I was under the impression that each client was a node, but I'm confused. So confirmations have to come from miners nodes only, correct?

The number of confirmations is the depth of the block containing your transaction in the blockchain. When you send a transaction it has '0' confirmation as it isn't contained in a block yet. When it's in a block it has one confirmation. When another block is found, on top of that one, then your transaction has two confirmations. etc.
 

Oh, ok. So it would need 5 new blocks found by 5 different miners in order for a transaction to have 5 confirmations?

Actually it could be the same miner finding new blocks, right?

It could be the same or new miners. Every new block counts regardless of who mined it.

Essentially yes but..

1) As pointed out, the blocks could be found by the same miner.

2) Some blocks may be orphaned.

Thanks.
So, if I understand correctly now, an attacker would have to overcome the hash power of the current miner(s)?

 I'm just trying to figure it out what would be the minimum arrangement that the protocol would work securely.

What you are referring to is called a 51% attack. It's one among a number of different attack strategies, see;

https://en.bitcoin.it/wiki/Weaknesses (https://en.bitcoin.it/wiki/Weaknesses)

A 51% attack has to do with total hashing power and not the overall number of nodes on the network.

I have a lot of "free" hours on Azure.  I run some wallets on some VMs in different geo-locations as "honest nodes".

My little contribution.