Dr. Dobb's Journal December 1999
While there's no question that cryptography is a science, you could argue that, like many scientific disciplines, it's also an art. What you can't dispute, however, is that with his sculpture "Kryptos," James Sanborn has wonderfully merged the art and science of cryptography. Located in the courtyard of the U.S. Central Intelligence Agency since 1990, Kryptos (Greek for "hidden") is a curved, scroll-like 10-foot tall copper plate with 2000 letters of the alphabet cut through it. The characters on the left side of the sculpture constitute a table (the "Vigenere Tableau," developed by the 16th-century cryptographer Blaise de Vigenere) for deciphering/enciphering the coded message. Those on the right make up the secret message that can be decoded using the table.
As you might expect, posting a coded message -- especially one 10-feet tall -- in the midst of the CIA is like waving a red flag in front of a Cold War bull. That's one reason cryptographers, mathematicians, computer scientists, and others have been trying to crack the secret code for nearly a decade. Still, only Sanborn, former CIA director William Webster, and possibly one other person knew the contents of the message -- until recently, that is.
After all these years, David Stein, a physicist and senior analyst at the CIA, has deciphered all but 97 characters of the message -- and amazingly he did it without a computer. Working at home in his spare time, Stein spent nearly 400 hours over several years working with pencil and paper. In a fascinating pair of interviews on abcnews.com (http://more.abcnews.go.com/onair/ worldnewstonight/wnt990618_stein_intv.html) and National Public Radio's "All Things Considered" (http://www.npr.org/programs/atc/990826.kryptos.html), Stein describes the methodology and thrill of breaking the secret code. According to Stein, Kryptos uses what appears to be a minimum of three encoding schemes -- substitution (where one character is substituted for another, but not always the same letter), transposition (where the characters are the same as in the plain text, but rearranged), and finally a mystery code(s). Stein broke the substitution code after discovering the pattern "DQM" in the first few lines of the plain text, then he went on to the transposition code. (The complete encrypted code, Vigenere table, and other information is available at the abcnews.com site.)
What Stein ultimately discovered was that the entire message is about 850 characters long; in deciphering the first two parts, he has about 768 characters comprising two messages. The first message is somewhat cryptic, starting out "Between the subtle shading and the absence of light lies the nuance of illusion," then going on to give the global coordinates for CIA headquarters. The second message is a quote from Howard Carter's The Tomb of Tut-Ankh-Amen (Dover Publications, 1977, ISBN 0-48-623-500-9), which describes the opening of King Tut's tomb.
Stein finds this quote significant since, like his unraveling of Kryptos, Carter went through multiple layers of secrecy to get into the tomb. But why this book? In the NPR "All Things Considered" interview, Sanborn said that The Tomb of Tut-Ankh-Amen is the most exciting book he has ever read, adding that Carter's moment of discovery is akin to "what cryptographers feel when they decode a message that's been hidden for years and so I chose that statement to demonstrate -- or really give the essence of -- the feeling of discovery."
As for the third coding scheme and the message hidden in it, Stein is as mystified as everyone else. But even though the last 97 characters:
OBKR
UOXOGHULBSOLIFBBWFLRVQQPRNGKSSO
TWTQSJQSSEKZZWATJKLUDIAWINFBNYP
VTTMZFPKWGDKZXTJCDIGKUHUAUEKCAR
remain unbroken, Sanborn isn't giving anything up. In fact, as Stein points out, there may be multiple layers of encoding that make the last part significantly more challenging than the first two. Sanborn hinted as much in the NPR interview, stating that "there are encoding systems which use patterns, light, and shadow, and it's those kinds of systems I was most interested in using because I'm an artist."
As impressive as Sanborn's sculpture is, what shines through is Stein's problem-solving ability. His methodology for cracking the Kryptos code involves looking at the facts, making careful assumptions about them, and keeping track of the entire process. Then when you go back and review what you've come up with, you can usually see where you went wrong. All in all, that's pretty good advice for solving all kinds of problems -- coded messages and otherwise.
Jonathan Erickson
editor-in-chief
jerickson@ddj.com