The Da Vinci Code

Many great minds in history had invented cryptologic solutions to the challenge of data protection: Julius Caesar devised a code-writing scheme called the Caesar Box; Mary, Queen of Scots created a transposition cipher and sent secret communiques from prison; and the brilliant Arab scientist Abu Yusuf Ismail al-Kindi protected his secrets with an ingeniously conceived polyalphabetic substitution cipher.

Da Vinci, however, eschewed mathematics and cryptology for a mechanical solution. The cryptex. A portable container that could safeguard letters, maps, diagrams, anything at all. Once information was sealed inside the cryptex, only the individual with the proper password could access it.

“We require a password,” Sophie said, pointing out the lettered dials. “A cryptex works much like a bicycle's combination lock. If you align the dials in the proper position, the lock slides open. This cryptex has five lettered dials. When you rotate them to their proper sequence, the tumblers inside align, and the entire cylinder slides apart.”

“And inside?”

“Once the cylinder slides apart, you have access to a hollow central compartment, which can hold a scroll of paper on which is the information you want to keep private.”

Langdon looked incredulous. “And you say your grandfather built these for you when you were younger?”

“Some smaller ones, yes. A couple times for my birthday, he gave me a cryptex and told me a riddle. The answer to the riddle was the password to the cryptex, and once I figured it out, I could open it up and find my birthday card.”

“A lot of work for a card.”

“No, the cards always contained another riddle or clue. My grandfather loved creating elaborate treasure hunts around our house, a string of clues that eventually led to my real gift. Each treasure hunt was a test of character and merit, to ensure I earned my rewards. And the tests were never simple.”

Langdon eyed the device again, still looking skeptical. “But why not just pry it apart? Or smash it? The metal looks delicate, and marble is a soft rock.”

Sophie smiled. “Because Da Vinci is too smart for that. He designed the cryptex so that if you try to force it open in any way, the information self-destructs. Watch.” Sophie reached into the box and carefully lifted out the cylinder. “Any information to be inserted is first written on a papyrus scroll.”

“Not vellum?”

Sophie shook her head. “Papyrus. I know sheep's vellum was more durable and more common in those days, but it had to be papyrus. The thinner the better.”

“Okay.”

“Before the papyrus was inserted into the cryptex's compartment, it was rolled around a delicate glass vial.” She tipped the cryptex, and the liquid inside gurgled. “A vial of liquid.”

“Liquid what?”

Sophie smiled. “Vinegar.”

Langdon hesitated a moment and then began nodding. “Brilliant.”

Vinegar and papyrus, Sophie thought. If someone attempted to force open the cryptex, the glass vial would break, and the vinegar would quickly dissolve the papyrus. By the time anyone extracted the secret message, it would be a glob of meaningless pulp.

“As you can see,” Sophie told him, “the only way to access the information inside is to know the proper five-letter password. And with five dials, each with twenty-six letters, that's twenty-six to the fifth power.” She quickly estimated the permutations. “Approximately twelve million possibilities.”

“If you say so,” Langdon said, looking like he had approximately twelve million questions running through his head. “What information do you think is inside?”

“Whatever it is, my grandfather obviously wanted very badly to keep it secret.” She paused, closing the box lid and eyeing the five-petal Rose inlaid on it. Something was bothering her. “Did you say earlier that the Rose is a symbol for the Grail?”

“Exactly. In Priory symbolism, the Rose and the Grail are synonymous.”

Sophie furrowed her brow. “That's strange, because my grandfather always told me the Rose meant secrecy. He used to hang a rose on his office door at home when he was having a confidential phone call and didn't want me to disturb him. He encouraged me to do the same.” Sweetie, her grandfather said, rather than lock each other out, we can each hang a rose—la fleur des secrets—on our door when we need privacy. This way we learn to respect and trust each other. Hanging a rose is an ancient Roman custom.

“Sub rosa,” Langdon said. “The Romans hung a rose over meetings to indicate the meeting was confidential. Attendees understood that whatever was said under the rose —or sub rosa—had to remain a secret.”

Langdon quickly explained that the Rose's overtone of secrecy was not the only reason the Priory used it as a symbol for the Grail. Rosa rugosa, one of the oldest species of rose, had five petals and pentagonal symmetry, just like the guiding star of Venus, giving the Rose strong iconographic ties to womanhood. In addition, the Rose had close ties to the concept of “true direction” and navigating one's way. The Compass Rose helped travelers navigate, as did Rose Lines, the longitudinal lines on maps. For this reason, the Rose was a symbol that spoke of the Grail on many levels—secrecy, womanhood, and guidance—the feminine chalice and guiding star that led to secret truth.

As Langdon finished his explanation, his expression seemed to tighten suddenly.

“Robert? Are you okay?”

His eyes were riveted to the rosewood box. “Sub… rosa,” he choked, a fearful bewilderment sweeping across his face. “It can't be.”

“What?”

Langdon slowly raised his eyes. “Under the sign of the Rose,” he whispered. “This cryptex… I think I know what it is.”

Chapter 48

Langdon could scarcely believe his own supposition, and yet, considering who had given this stone cylinder to them, how he had given it to them, and now, the inlaid Rose on the container, Langdon could formulate only one conclusion.

I am holding the Priory keystone.

The legend was specific.

The keystone is an encoded stone that lies beneath the sign of the Rose.

“Robert?” Sophie was watching him. “What's going on?”

Langdon needed a moment to gather his thoughts. “Did your grandfather ever speak to you of something called la clef de voite?”

“The key to the vault?” Sophie translated.

“No, that's the literal translation. Clef de voite is a common architectural term. Voite refers not to a bank vault, but to a vault in an archway. Like a vaulted ceiling.”

“But vaulted ceilings don't have keys.”

“Actually they do. Every stone archway requires a central, wedge-shaped stone at the top which locks the pieces together and carries all the weight. This stone is, in an architectural sense, the key to the vault. In English we call it a keystone.” Langdon watched her eyes for any spark of recognition.