BOSTON — The information needed to decipher the last remaining unsolved secret message embedded within a sculpture at CIA headquarters in Virginia sold at auction for nearly $1 million, the auction house announced Friday.

The winner will get a private meeting with the 80-year-old artist to go over the codes and charts in hopes of continuing what he’s been doing for decades: interacting with would-be cryptanalyst sleuths.

The archive owned by the artist who created Kryptos, Jim Sanborn, was sold to an anonymous bidder for $963,000, according to RR Auction of Boston. The archive includes documents and coding charts for the sculpture, dedicated in 1990.

Three of the messages on the 10-foot-tall (3-meter) sculpture — known as K1, K2 and K3 — have been solved, but a solution for the fourth, K-4, has frustrated the experts and enthusiasts who have tried to decipher the S-shaped copper screen.

The artwork resembles a piece of paper coming out of a fax machine. One side has a series of staggered alphabets that are key to decoding the four encrypted messages on the other side.

One person has contacted Sanborn regularly for the past two decades in an effort to solve K4, and Sanborn received so many inquiries he started charging $50 per submission. Sanborn decided to sell off the solution to K4, putting it in the hands of someone he hopes will keep its secrets and continue interacting with followers.

RR Auction said the winner will get a private meeting with Sanborn to go over the codes, charts and artistic intent behind K4 and an alternate paragraph he called K5.

The purchaser’s “long-term stewardship plan” is being developed, according to the auction house.

Sanborn’s roughly 50 public sculptures include a memorial for a 2019 mass shooting in Odessa, Texas.

The archive auction was almost derailed in September when two Kryptos sleuths found Sanborn’s original scrambled texts in the artist’s papers in the Smithsonian.

The sale went ahead but was changed from offering only the secrets to K4 to selling his entire archive.

“The important distinction is that they discovered it. They did not decipher it,” Sanborn told The Associated Press. “They do not have the key. They don’t have the method with which it’s deciphered.”