Suppose you wanted to bet on the outcome of a future bitcoin hard fork, how would you go about doing that?

That very question came up last spring on BitcoinTalk when Roger Ver, the controversial investor and proponent of a particular brand of bitcoin scaling, gave a nod to a challenge from another investor. The wager? Which of two blockchains would be more valuable if bitcoin were to split.

The challenge sought to speculate on the future of Bitcoin Unlimited (BU), a proposal for removing the bitcoin block size limit. (This was before SegWit2x came into play, although both protocol upgrades propose bigger blocks and require a hard fork to implement.)

Intrigued by the bet, and the amount of money Ver was willing to put on the table ($120m-worth of bitcoin at the time), researchers Patrick McCorry at University College London and Ethan Heilman at Boston University, along with Andrew Miller, assistant professor at University of Illinois, put their heads together to figure out a solution.

And to that end, they have released a paper outlining the technical details needed to carry through with the wager.

The wager

Before explaining how that protocol works, though, let’s go back to the bet.