The top secret code behind Kryptos, the infamously enigmatic sculpture with four hidden messages that stands at the CIA headquarters, is hitting the auction block in November. Artist Jim Sanborn’s original handwritten code, as well as a “proof-of-concept” prototype for the artwork and other items, are expected to fetch between $300,000 and $500,000, according to RR Auctions. The artwork has gained a cult following as one section of its encrypted text has remained unsolved since the sculpture deb...