Signal from the Lighthouse - UPDATED WITH ANSWERS

— 4 minute read

Challenge

THE CHALLENGE IS NOW CLOSED, READ ON TO SEE THE ANSWERS!

You are one of the few remaining humans on Earth. On an uneventful night, you sit still and observe the dusty dunes of what used to be a lake; evaporated from the nuclear blasts. The light from the lighthouse far away on the hill looking out onto the dunes is the only distraction to your eyes.

You observe that the light from the lighthouse sweeps past your vision in a strangely periodic manner: quickly twice, double blink, then once…then pause, quickly twice then pause... once, double blink, once…then pause and once again. This cycle repeats continuously. Seeing as this is a strange event, you jot down the pattern, and head back to your tent for the night.

..-. .. .-. .

The next morning you wake up and pack your things in preparation to continue your journey. As you walk past the same spot where you observed the lighthouse last night, you notice its light is fixated on a small stone slab out in the dunes. Curious, you walk over and observe letters on the slab, however they don't appear to resemble anything meaningful:

KZFQ QQXLYPFYXM JIJS GSQIIMX CEXNT III XZPQII

Recalling your experience with ciphers before the war broke out, you realize that this gibberish is probably an encrypted message, which requires a "key" to decipher. You pause in your journey to ponder how you could crack this code...

Afterward

After thinking for a while, you suddenly realize that those periodic movements were Morse Code! Recalling your education on ciphers, you manage to decipher the signal into a single word:

FIRE

You begin to think… That word must be used for something, I wonder if it is connected to the gibberish on the slab… it could possibly be the key to the encrypted message! And A cipher which requires a word as a key… that must make it a Polyalphabetic Cipher! You attempt the decipher the encrypted message and obtain

FROM LIGHTHOUSE SEEK POLARIS UNTIL RED PILLAR

You solved it!

As you read over the message a few times, you notice a few key words: POLARIS, and RED PILLAR. Polaris is likely referring to the Northern Star, which is often used as a guide due to its relatively fixed position in the night sky. It seems as though I will have to wait until night, and attempt to walk towards the direction of Polaris, from the base of the lighthouse.

Later that night, you begin your journey for what you hope is something that will help your kind; following the exact instructions described in the message. You walk and walk until you eventually come across a forest of tall, ragged stones. You cry out in joy, but then wonder, how am I supposed to know which pillar is the right one? None of them seem red to me…

At that moment, the sun began to rise; illuminating the pillars with warm, amber light. However, one pillar was different from the rest, as it appeared to contain speckles of glinting metal which reflected the fiery morning light into your eyes. Approaching that pillar while shielding your eyes, you kneel at the base of the pillar and notice what appears to be a well-hidden cavity within the pillar. Reaching into it you feel what appears to be a trigger and activate it, causing the ground nearby to open up and reveal a staircase into the ground. Hesitantly, you follow the staircase down and are met with the gaze of countless human eyes. A older person in the middle of the group approaches you, hands you a strange-looking alien device, and says:

“Welcome... to the Cryptography Project!”

To be continued...