Bitcoin Gold

• 1. Introduction

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  Bitcoin Gold broke away from the bitcoin blockchain on the 24th of October 2017. The split was framed as a fix for a problem drifting through the cryptocurrency world: mining had stopped being something an ordinary computer could do. Bitcoin Gold promised to change that by rewriting the rules of who could mine it. What that promise cost, and who ended up paying for it, is what this documentary traces.

• 2. A Fork Against ASICs

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  Application-Specific Integrated Circuits, machines built only to mine bitcoin, were the target Bitcoin Gold's creators set out to defeat. Bitcoin Gold's hard fork changed the proof of work algorithm so those specialized chips could no longer mine its blockchain. The hope was that mining would move back onto commonly available graphics cards, letting anyone mine from a home PC.

  Mashable, covering the launch, reported that Bitcoin Gold had been criticized for being hastily put together. The criticism also pointed to a developer pre-mine, coins set aside for the team before the currency reached the public. Shortly after launch, the project's own website was knocked offline by a distributed denial of service attack.

  A blockchain that can be mined by anyone can also, it turned out, be attacked by anyone who gathers enough of that same computing power.

• 3. Twice Compromised

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  In May 2018, an unknown actor carried out a 51% hashing attack against Bitcoin Gold. Controlling the majority of a blockchain's mining power lets an attacker rewrite its transaction ledger and spend the same coins twice. During this attack, 388,000 BTG, worth approximately US$18 million, was stolen from several cryptocurrency exchanges. Bittrex, one of those exchanges, later delisted Bitcoin Gold after its team refused to help pay some of the damages.

  In July 2018, Bitcoin Gold's developers switched to a new mining algorithm that demanded more memory. The change was meant to discourage ASIC mining further, pushing back once again against the same hardware the original fork had tried to shut out.

  January 2020 brought a repeat: Bitcoin Gold suffered another 51% attack. By July, the team pushed out version 0.17.2 as an emergency update, meant to escape a long attack chain that had begun a few days earlier. It shipped as a defensive patch, a small piece of code standing between Bitcoin Gold and the next attempt to rewrite its ledger.