The bitcoin white paper is 15 years old. Here's what it is and who people think its mysterious author could be.

• The bitcoin white paper was published 15 years ago by Satoshi Nakamoto.
• The paper outlined the blockchain technology that would underpin a decentralized payment system.
• The pseudonymous author has never been identified, though there are theories as to their identity. 

At the end of October 2008, an unidentified individual or group on people under the pseudonym Satoshi Nakamoto published a paper to a mailing list called Metzdowd titled, "Bitcoin: A Peer-to-Peer Electronic Cash System."