Quote from: WaPTS on December 02, 2013, 02:25:00 am

Quote from: bytemaster on December 01, 2013, 07:24:24 pm

I am really looking for attacks on my pos system


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can we develop a system to avoid the 51% attack totally , I have some thinking , in democratic society, one person have  larger  power and he only have one vote,  a node have larger power of hash ,it is only mean  he have the larger capacity for mining,  not the larger power of main chain,
we can think as following
1. one node cannot find two continuous bolck
2. the difficulty of every node is different,  for example if the node not find the bolck in 10min , the difficulty is same as the normal  difficulty, but if the node can one bolck in 10 min the difficulty become the 2*normal difficulty ,  if find 3 bolck in 10min ,the difficulty become the 4*normal difficulty , and so on ,   if we need to 6 bolck confirm , though a man have 51% power of hash , he also cannot carry out 51% attack.

There is no way to identify nodes, all we have is 'information'.   Difficulty is irrelevant because proof-of-stake determines longest block and nodes cannot cheat this.   Just like any company where a shareholder who owns 51% of the stock can do anything they want (more or less), the same applies to DACs.   There is no way around the 51% ownership attack in a world subject to sybil attacks.

It seems that individual difficulty can indeed be used to avoid sybil attacks, as I decribe in my post https://bitcointalk.org/index.php?topic=1702796.0. While you cannot prevent an 51% ownership attack under any circumstances, you can make it economically unattrative so that no rational attacker would attempt it.