Bitcoin’s Future Depends on a Handful of Mysterious Coders

Andrew Chow started tinkering with bitcoin in high school. Unknown to his parents, and before he even had a bank account, the teenage coder set up a website that said “I will work for bitcoin” and provided a wallet address for people to tip him.

Seven years later, Mr. Chow is one of a handful of people who can write changes into the software that underpins the nearly $500 billion cryptocurrency. Their role is critical to bitcoin, yet is largely unknown to the millions who own it.