Petrology

How It Works

Both of the sheets of paper are independently solvable – so teams could have solved both in parallel to save time.

The first sheet, which refers to the eavesdropping relay,  contained a cryptogram encoded using the simple atbash cipher.  (An atbash cipher is a substitution cipher that consists of the reversed alphabet.)  The cryptogram was solvable through cryptanalysis, but teams could save significant time if they realized a series of codewords were an anagrammed clue (Severer <> Reverse, Pale Bath <> Alphabet, Sue <> Use, Sit Tutu Bison <> Substitution, and ReChip <> Cipher).  The ciphertext decoded to:

USE A LOW COST CHARGE COUPLED DEVICE SUCH AS A CELL PHONE CAMERA TO SEARCH FOR THE RELAY.  THE RELAY WAS LIKELY STORED NEAR (BUT NOT INSIDE) THE CLEARVIEW NURSERY SHOWROOM IN PLAIN SIGHT.  ONCE YOU FIND THE DEVICE, TRANSCRIBE ITS MESSAGE FOR FURTHER ANALYSIS INSTRUCTIONS.

The second sheet, which contained the garden map, is a classic battleship puzzle.  A battleship puzzle consists of a grid in which a number of “ships” are placed such that they satisfy numeric constraints on the number of ship segments that are in each column and row.  In this case, the ‘ships’ were actually garden surveillance devices, and three were already placed in the grid to provide a starting point for solving the puzzle.   An additional rule that helped place the devices was that each ‘ship’ has a one square border around it where no other devices were placed.

Once teams decoded the ciphertext, they were to begin searching for the eavesdropping relay.  The relay was actually a large papier-mâché rock that was sitting on the porch of the nursery showroom.  When a cell phone camera is used to view the rock, an array of embedded infrared lights brightly illuminates the phone’s screen.  The lights are blinking on and off, broadcasting morse code for CQ (morse shorthand for the beginning of a message) followed by a telephone number.

Solution

Calling the telephone number prompted teams to enter the coordinates of all of the segments from the garden map.  Entering these coordinates properly resulted in an overheard conversation with a mob flunkie (expertly voiced by Raggs) that gave teams the solution word, “unicorn.”

Design Notes

  • Originally, the puzzle was constructed out of 880nm infrared LEDs.  These LEDs are near-IR, however, and were barely visible to the naked eye as a faint red glow.  Switching to 940nm devices completely solved that problem (although I had to try two different models of LEDs before I found ones that were bright enough)
  • The puzzle was not always located at Clearview Nursery (which influenced some of the design elements of the puzzle – the Garden Map part of the puzzle themed a lot better when it used to be an actual battleship puzzle :)).  It was explicitly moved there to take advantage of the darkness of nighttime so the IR LEDs would be easier to see.
  • Because the rock was constructed out of newspaper, cardboard, and electronic things, the constant rain throughout the weekend forced a late-breaking change to move the rock onto the porch of the showroom where it could be sheltered.  (The original plan was to hide it better in one of the large piles of rocks that Clearview Nursery sells.)
  • The fine folks at Intern Puzzle Day really came through for us by allowing us to borrow the acting talents of Fake Rock (also known as Stone 2.0) for this puzzle.  Our initial attempt at producing a fake rock out of insulation foam produced something that looked more like a collapsed cheesecake than a rock, so Fake Rock’s onstage grace and presence was much appreciated.
  • The telephone system had built-in protection against brute forcing the battleship puzzle too quickly – if you called too frequently from the same phone number, it would forcibly disconnect you.  Call logs indicate some teams solved the puzzle in one or two calls to the phone system, while others repeatedly called waiting for the brute force protection to disengage so they could get another clue :)

GC Notes

The phone number was encoded with parentheses, which caused minor confusion for some teams because parentheses aren’t always found on morse code charts.

The location was unstaffed, in large part because a staff member would make it more obvious that there was a device planted onsite at the nursery.  Unfortunately, word on the street is that at least one team disassembled the control box and used the diagnostic LED from the relay board that controlled the light array to solve the puzzle.  Future puzzles like this will probably need to be staffed to prevent teams from dishonestly tampering with the clue.