Bitcoin Forum

Hi everyone as a new member (and a French one ;) I post here on the newbies section.

In a science project (crypto security) I'm trying to emulate someone trying to redo a proof of work starting at a define block and trying to catch up with the network current state. I'm browsing the web for tools aiming to build such a proof of work but I can't seem to find anything useful. Thanks in advance for your help.

u wana overtake the current bitcoin chain from a previous block that got beat? ;o

I want to take a previous block and see the cost of catching up with the current longest chain. To determine feasibility.

Since you only want to emulate, you don't need to execute the actual proof of work (hashing).
The scenario you're describing is the classic 51% attack. Basically, an attacker needs to have more hashing power than all other hashing nodes in the network combined. For each block mined, the probability that the attacker will mine a block in his own chain is roughly proportional to his relative hashing power.
So if your attacker can divert the hashing power of more than half of all miners (which means he would have to usurp the biggest mining pools), he could theoretically do it. Alternatively, he could buy ASIC chips totalling a bit more than the current worldwide hashing power to gain 51% hash performance.

Both of these attacks would not go unnoticed, so in addition to the simple costs of the attack, the attacker would have to deal with the effects which would likely more than offset his possible gains.

Onkel Paul

Do you want to actually emulate it, or do you only need proof it is possible?

Thanks for your kick response.

@OnkelPaul I was aware of this "trouble" with the attack but we are actually investigating every aspect of this attack. In particular in the Nakamoto first paper describing Bitcoin it was imply that it could be interesting for someone owning 51% of mining to mine in order to get new coins vs trying to overrun the system.

@Slartibartfast from M.
I actually want to emulate a part of it (for example the 100 firsts blocks) in order to collect some data time of execution, CPU/electricity costs and other things.

Thanks in advance.