[1001101]

Quick thought experiment: I just did a quick back of the envelope calculation on the brute force approach. 50% of the current hash rate would be 548 million retail - (current rate 8M TH/s, 1850$ retail Antminer S9 rated 13.5 TH/s). That's a quick thought on naive approach - not sure I have that right, so please check my work. I have a few other ideas as well. edit: of course, the existing hash rate would still be there, so you'd have to double it, not buy half. I still think the retail estimate is on the high side (markup, not leveraging economies of scale). My guess is that an organization like DARPA could buy Bitcoin for <250M$.