If you’re a big fan of the blockbuster thriller “The Da Vinci Code,” you might already have heard something about “Kryptos,” the enigmatic sculpture that sits in the courtyard of the Central Intelligence Agency’s headquarters in Langley, Va.

Perhaps you’ve visited the Web sites of the author, Dan Brown, and his publisher, Random House Inc., which hint tantalizingly that the code-covered CIA statue that has baffled some of the world’s best cryptographers for 15 years now may figure into the plot of the upcoming sequel about the mind-bending exploits of Harvard symbologist Robert Langdon.

What you couldn’t know, however, is that the man who claims to be the first to crack and partially solve two of the three cryptographic systems necessary to decipher Kryptos’ wily, obscure riddle is Richard Gay, a Maine native and retired CIA operative who lives in Blue Hill.

And now that the supposed connection between “The Da Vinci Code” and Kryptos has caused something of a code-breaking frenzy among professional and amateur cryptographers eager to finally solve the entire puzzle, Maine’s self-styled “old spook” said he would like to get the credit he deserves for his early work.

“Kryptos is now a growth industry,” Gay said Tuesday while sitting in the snug study of his 1860s-era home, which he and his wife run as a bed-and-breakfast. “I know I’m going to be recognized publicly for breaking into the code, because I intend to work at it until I am.”

After graduating from the University of Maine in 1957, Gay, who speaks 12 languages, spent nearly 20 years in the intelligence field. Beginning his spy career at the National Security Agency, he moved to the CIA in 1960, where he spent the next 15 years as a covert operative in clandestine services.

In April 1997, while on a visit to the CIA’s closely guarded campus, Gay got his first look at the mysterious Kryptos.

“My wife and I were sitting in the cafeteria with a couple of CIA people when I saw the sculpture out in the courtyard and asked what the heck it was,” Gay recalled. “It was a cryptogram, and I was told no one had broken it yet.”

The sculpture was created by the Washington, D.C., artist James Sanborn using complex code systems devised by Ed Scheidt, the retiring chairman of the CIA’s Cryptographic Center.

Intended as a whimsical challenge to CIA staffers, the large, stylized copper scroll contains a dense matrix of 1,800 or so letters cut into its half-inch verdigris facade.

Intrigued by the puzzle, Gay went into the courtyard, which is off-limits to the public, and scanned the ribbon of letters for clues. Inscribed on the right side of the sculpture was a Vigenere Tableau, a well-known 16th-century system of code tables that substitutes letters throughout a message, shifting from one alphabet order to another with each letter. Gay knew it had to have been put there to be used in the decoding process. On the left was the encrypted message, it’s devilishly difficult secrets waiting to be revealed.

He then got a pencil and paper and copied the coded characters inscribed on the top section of one of the sculpture’s panels. Back in Maine two days later, he called his friends in the intelligence service, as well as the sculptor himself, and asked that they send him transcriptions of the letters on the bottom half of the section.

“I couldn’t wait to get out my graph paper and pencils and get at it,” he said. “I’m an old-style cryptanalyst. That’s what the NSA does – codes and ciphers. It’s part of my former trade, and I wanted to break it.”

As he labored through that first night, using classical deciphering methods, Gay found enough repeating patterns among the letters to know it was just a matter of time until he made a breakthrough.

His first break came when his assumption that the three-letter repeat D-Q-M represented T-H-E turned out to be correct. He now had recovered from the matrix the most common word in the English language, THE, as well as the most frequently occurring letter, E.

After more than 40 hours of intense work, littering pages of graph paper with his dogged efforts and recovering a number of valuable word bits from the sea of jumbled letters, Gay was able to determine that there were three Kryptos code systems at work. For the benefit of those of you who may be crypto-inclined, the three systems are: polyalphabetic substitution, a scrambled English language known as a transposition, and a critical third one still to be discovered.

When he was unable to match any of the U letters with the lone Q in the transposition section – a U will always follow a Q in an English word – he surmised that the Q must stand alone as a space filler or as a question mark at the end of that section.

Although his progress was limited, Gay was excited enough to inform the CIA’s public affairs people and ask that they post his Kryptos work in the agency’s bulletin.

He also offered to team up with any agency employee interested in helping him tackle the unsolved final section with a computer. While he got no takers, he said, news of his accomplishments jump-started the CIA’s interest in cracking Kryptos.

Lacking “machine support” to perform the endless drudgery of counting the occurrence of each letter and doing statistical analyses of the counts, Gay was forced to shelve his quest to solve the Kryptos puzzle. He and his wife were preparing for their first season as innkeepers that year, which left little time for such joyful pursuits as breaking a code that had no bearing on national security.

Gay’s success was noted in the spring 1998 issue of the Phoenician, the NSA’s in-house organ. He also wrote a lengthier account the next year for the newsletter of the Association of Former Intelligence Officers.

Shortly after Gay submitted his article, however, the CIA published in its newsletter the Kryptos achievements of a physicist on staff named David Stein. In the winter of 1998, after more than 400 hours of work with only pencil and paper, Stein had managed to decipher all but the last 97-character section of the message that had eluded so many for so long.

The first part of the message reads: “Between subtle shading and the absence of light lies the nuance of iqlusion.” As if the cryptogram was not difficult enough, the artist had complicated matters even more by intentionally misspelling “illusion” and a few other words.

The second part includes the latitude and longitude of the CIA’s headquarters – parts of those coordinates are said to be hidden in the cover design of “The Da Vinci Code” – and the line: “Does Langley know about this? They should: it’s buried out there somewhere. X Who knows the exact location? Only WW.” The initials are assumed to refer to former CIA chief William Webster.

The next part was taken from archaeologist Howard Carter’s account of opening King Tut’s tomb: “Slowly, desparatly slowly, the remains of passage debris that encumbered the lower part of the doorway was removed. With trembling hands I made a tiny breach in the upper left-hand corner. And then, widening the hole a little, I inserted the candle and peered in. The hot air escaping from the chamber caused the flame to flicker, but presently details of the room within emerged from the mist. X Can you see anything?”

When California computer scientist James Gillogly came up with the same message by attacking the code with a PC that ran programs of his own design, his 1999 announcement on the Internet introduced Stein’s achievements – and Kryptos itself – to the outside world.

Now with the world’s best cryptographers, including former KGB spies, racing to crack Kryptos’ final 97-character section from transcripts on the Internet, Gay also would like to have his early breakthrough recognized by more than just his peers in the intelligence community.

“I’m seeing my words, my theories and my clues all over the Internet these days, but I don’t see my name attached as a source to anything,” Gay said.

Aside from his writings in several intelligence-community periodicals, he has never gone public until now about the role he played in the mystery. For an old cryppie like Gay, it’s become a matter of professional pride.

So he’s been building his own Web site, www.kryptos-cia.com, and posting on it all of the old Kryptos-related files he has kept in the attic in Blue Hill. Gay has also resumed his quest to unlock Kryptos’ secrets from that final section, that cryptographic Holy Grail, and he has a few ideas that he intends to test when he visits the CIA campus again this fall.

He won’t reveal too much, of course, except to suggest teasingly that the play of sunlight and shadow around the statue might factor into the solution. Then again, the old spook might just be putting would-be competitors off the scent.

But even if he could manage to break out the entire message, will it then lead to another code that must be solved, which leads to another, like peeling back the layers of an onion?

The questions seem endless, including this one: If Kyrptos does figure into “The Da Vinci Code” sequel, as so many have speculated, how will the book’s brilliant protagonist ever get near the sculpture?

“If he does get inside that courtyard,” Gay said, “he’ll be surrounded by seven stories of secret agents peeking out the windows at him.”