Satoshi Found: Perplex City Just Got A Little Less Perplexing

It’s been almost fifteen years since Andy Darley entered Wakerley Great Wood in Northamptonshire with his trusty trowel in hand and dug up the Receda Cube, ending the first season of Mind Candy’s alternate reality game Perplex City and claiming the game’s £100,000 prize. While the game’s main narrative was solved with the discovery of the cube, some of the game’s most ardent fans continued to chip away at the game’s unsolved puzzles, designed to be nigh impossible. And on December 30th, the final puzzle was solved when players got in contact with a man based on nothing more than a single photo, and a first name: Satoshi. After over a decade, the puzzle Billion to One has been solved.

A Brief Perplex City Primer
Perplex City was an alternate reality game that launched in 2005, whose story unfolded through a series of collectible puzzle cards. According to the game’s lore, Violet Kiteway stole an object known as the Receda Cube from the Perplex City Academy Museum. After being teleported to our world, she buried the Cube and posted cryptic messages hinting at its location under the name “Combed Thunderclap”.

Not knowing his own daughter was the thief, Perplex City Academy Master Sente Kiteway partnered with Mind Candy to release a game: Perplex City. The game was designed to let people of Earth learn about their world and the theft, with the hopes that Earth’s puzzle-solvers could figure out what their Perplexian counterparts could not. And so, 256 puzzle cards were released into the world in four separate waves.

Clues on the cards might lead players to websites, blogs, emails, and telephone numbers, and a San Francisco live event even had one character escape the scene in a black helicopter…but for many, the heart of the game were puzzle cards themselves: every card had a silver scratch panel hiding a unique code that players could use to track their solves, powering a live leaderboard. Three puzzles were particularly notorious for being unsolved.

A Herculean Task: An Introduction to the Unsolved Cards
Difficulty levels of the 256 Perplex City puzzle cards were sorted into eight different difficulty levels. From easiest to hardest, those levels are: Red, Orange, Yellow, Green, Blue, Purple, Black, and Silver. By the time Darley found the Cube, most of the Silver puzzles had already been solved.

Card #238, Riemann, challenged puzzlers to prove the Riemann hypothesis, one of the seven Millennium Prize Problems, a series of mathematical problems flagged by the Scientific Advisory Board of the Clay Mathematics Institute as some of the most difficult problems mathematicians were grappling with at the turn of the millennium. The institute offered a $1 million bounty for solving any of these problems. While Riemann remains unsolved, this was the only puzzle in the set that was designed without a solution in mind.

Card #251, The Thirteenth Labour confronted players with a string of 352 characters encrypted with RC5.64 cipher that was expected at the time to take 30K computers running in tandem for several months to solve. Players dubbed their attempt to crack the RC5 encryption “Assault on 13th Labour“, although ultimately the user Paraboloid13 who cracked the password in Feburary 2010. While Paraboloid13’s solution was verified as correct, they declined to share either answer or method of solve publicly, leaving the final mystery of this herculean task preserved.

Card #256, Billion to One presented players with a photograph of a man, and the text 私を 見つけなさい – “Find Me”. The Perplex City hint line gave players their only other clue: the phrase “My name is Satoshi.” Players located the photograph’s location of Kaysersberg France, but hit an Alsatian wall for years. Once a player directly contacted Satoshi, he was instructed to provide them with a password in response to successfully solve the puzzle.

The Search for Satoshi: It’s Not So Small a World After All
Long after The Thirteenth Labour was cracked, the story of the Billion to One puzzle card kept coming back, reigniting the search for Satoshi. During the early years of the search Chris Warren’s Billion2One.org offered a shareable multi-lingual page to help attract more eyeballs to the search, while Laura E. Hall’s FindSatoshi.com provided a summary of the hunt, and the community’s progress.

Word of the search spread through podcasts, YouTube video essays, and news coverage, but no additional leads arose. But earlier this year, Inside A Mind’s Jamie Foster released a video summarizing the search that received over 1.2 million views along with a companion podcast interviewing Hall about the search that inspired the creation of the r/FindSatoshi subreddit. And that triggered the break in the case.

Tom-Lucas Säger (th0may on Reddit) remembers watching the Inside A Mind video earlier in the year, but put it out of his mind, because he couldn’t believe it was possible. While visiting his parents for Christmas, he remembered the story, noting:

I told [my parents] about it and later wondered if it was solved. That was when I found out about the subreddit and I thought, “if they are still actively searching maybe give it a try”. I’m currently doing a research project on AI and Design and stumbled upon a backwards image search that uses facial recognition…[called] PimEyes.

After running the card’s picture through the tool, Säger uncovered a 2018 photograph of a man drinking a beer at a summer festival who bore a striking resemblance to Satoshi, and posted it to the subreddit. Since the photograph was posted to a company website, that led to confirmation that his first name matched.

After initial outreach did not generate a response, Säger got in contact with Hall, who worked with a friend in Japan to send a follow-up email in English and Japanese, leading to confirmation that they found the right Satoshi. Reacting to the news, Perplex City co-creator Adrian Hon tweeted, “I thought [Billion to One] would either be solved very quickly (within a year or two) or not at all. To have it solved after 14 years is very special.”

And it’s telling that the solutions to The Thirteenth Labour and Billion to One cards benefited from advancing in computing. For The Thirteenth Labour, it was likely an exercise of Moore’s Law in action: . For Billion to One, it’s telling that this was not solved through a victory of the small world phenomenon in action, but one that was supported by facial recognition nuanced enough to connect photos of the same man, taken over a decade apart.

The Most Dangerous Game: Knowing It’s Time to Stop the Hunt
Since Billion to One, a number of experiences have toyed with the idea of turning a nationwide manhunt into a game. In 2009, DARPA deployed ten weather balloons across the United States and awarded the first team to correctly identify every location with a $40K prize. That same year, Wired pitted journalist Evan Ratliff against the internet in a nationwide manhunt, for a $5K prize to the first person to track him down. As ARGNet’s coverage of The Hunt for Evan Ratliff notes, the practice pre-dates the internet by a considerable margin, with the Westminster Gazette running a manhunt for one of the company’s employees, who assumed the name Lobby Lud for the purposes of the contest.

However, and this should go without saying, manhunts should be handled with care, for the safety of both hunter and hunted. As one article about the Lobby Lud affair by Paul Slade notes, “Lud lookalikes were having a rough time of it…with one man reporting he had been accosted seven times in just 20 minutes – despite the fact that he was nearly a foot taller than the real Lobby.” At least based on currently available information, the Find Satoshi community exercised admirable restraint in limiting outreach to make this final leg of the race minimally intrusive, and that level of respect should extend now that his involvement has conclusively ended.

This warning is particularly relevant since, while Satoshi shares a first name with Bitcoin founder Satoshi Nakamoto, that is where the similarities end: Perplex City‘s Satoshi is not Bitcoin’s Satoshi. Billion to One launched years prior to the release of Nakamoto’s whitepaper, and it is an exceedingly common name in Japan. Echoing a sentiment that Hall expresses on the Find Satoshi website, now that the puzzle has been solved and Satoshi’s identity has been revealed, please don’t contact him – “his agreement to participate in [Perplex City] was limited to this one puzzle, and that is now complete.”

As additional updates to the story arise, you can likely find them on FindSatoshi.com, as well as r/FindSatoshi. Congratulations to everyone who has chased after the solve over the years, and a hearty thanks to Tom-Lucas Säger (th0may) for closing the chapter on a mystery I never thought I’d see solved.

UPDATED TO ADD: Now that the cat is out of the proverbial bag, puzzle designer Jey Biddulph has started sharing behind the scenes insights about the puzzle creation process on Twitter.

Disclosure: Michael Andersen (the author of this piece) works for Tiller Press, which will be publishing Laura E. Hall’s book on escape rooms in 2021.