Kryptos

Kryptos is a sculpture by Jim Sanborn in copper, petrified wood, stone, water, and plants. It was dedicated in 1990 and situated at CIA headquarters in Langley, Virginia. It contains at least five ciphers. The first three, K1 - K3, were solved in the 1990s, though it has been said that they were not solved as intended. K4 is unsolved. The ciphertext of K5 is said to emerge with the solution of K4, so it is both unknown and unsolved.

Here’s a PDF showing the Kryptos characters, with a font and kerning that closely matches the sculpture.

The following are snapshots of current work, followed by some thoughts about the way in.

FORCE RANT
GREYISH IMAGE EAST NORTHEAST
HEELS TEAR
TAMPER BLOWS STONE SEAL
BERLIN CLOCK
FORCE INCREASE
ENDEAR LOVE 

FORCE RANT
GREYISH IMAGE EAST NORTHEAST
HEELS TEAR
NUCLEUS REND STONE SEAL
BERLIN CLOCK
FORCE INCREASE
ENDEAR LOVE

UEOSFOMJDDEYUMIOISIRYHDRGEBHHKEQ
‍___________HXУOЫЙAOЦЧMXЧЙЧДПУCФЮЗ
XHЖPБЫЖЦФЪБCЧPПMЦЧШTXККЖПЩЗПЙXГO