Question: "Communications intelligence" has come a long way since the Code Talkers of World Wars I and II, when Native American languages were encoded to befuddle the enemy. How do computers today encrypt secret messages on hard drives, radio, even e-mail, and how likely are these to be broken?
Answer: Three standard tricks are substitutions, permutations and secret keys, often used in combo, says University of Pittsburgh professor of information science and telecommunications Michael B. Spring.
Substitution: Take "hello how are you" and "rotate" the letters by adding two so an "a" becomes a "c," "c" an "e," etc. The message becomes "jgnnqbjqybctgb qw" — note the y rotated to the end space between z and a of the next abc . . .
To decode you need to figure the rotation and reverse it.
Permutation: You write the message in, say, a 4x5 matrix, then code by reading it out vertically:
hell (4 slots across, 5 down)
o ho
w ar
e yo
u
The three spaces after the "u" round out the 4x5 box.
To create the cipher (coded message), you read down the box, getting "howeue lhay loro." To decode, you write the cipher in a box vertically and read it out horizontally, but you need to know the dimensions of the box that was used. Now combine these in complex ways, explains Spring, throwing in a "secret key" that randomly reassigns letters, and the code becomes difficult to break.
"If it's an encrypted message between you and your buddy about the school dance, who would spend time and money to decode? But if you're selling national secrets, it is probable that with time, the code could be broken."
Question:Would a hard-riding warm-weather cyclist fatigue faster in a roadrace or pedaling a stationary exercise bike?
Answer: The latter will "do in" a rider sooner because the lack of headwind breeze makes it tougher to cool the body, says Oxford physiologist Frances Ashcroft in "Life at the Extremes: The Science of Survival." This has startled competition cyclists brought into a test lab, who petered out rapidly despite enduring grueling 12-hour uphill stretches in races. Turn a fan on the static bikers and they last much longer.
This phenomenon may be behind the occasional instances of heatstroke when a cyclist or runner finishes exercising abruptly, as well as the horseman's old maxim to be sure to cool a horse down after a hard workout.
Question: Is self-powered flight possible using space-age materials and design and top-conditioned modern athletes, realizing Leonardo da Vinci's ancient dream?
Answer: Actually, it's been done, sort of, in the 1970s when the "Gossamer Albatross," with a bicycle-style drive system fitted to a lightweight skeletal propeller aircraft, achieved liftoff, say Susan M. Lea et al. in "Physics: The Nature of Things."
The pedal-and-crank system powered by a rapid sequence of muscle bursts was ideal to the task. In 1979, the Albatross was flown across the English Channel in 3 hours with the pilot averaging about 1/3 horsepower output for the 22 miles. An average person can do 1 horsepower briefly, such as for running up stairs, but achieving 2/3 horsepower for an hour requires a world-class athlete.
Leonardo and countless other flight-fanciers over the centuries had envisioned not bikes but strong-armed men with artificial wings affixed, flapping into the sky. This is not likely to happen soon, but bird-like "ornithopters" are on various drawing boards, such as that of University of Toronto aerospace engineer James DeLaurier, who has designed an engine-powered version. "Arm power alone would never suffice, but if the flapping-plane were of lightweight carbon fibre and Kevlar and the setup allowed arm, leg and back muscles to exert in a vigorous rowing motion, and if the operator got up into top, top condition . . . well, da Vinci's dream just might take wing."
Send STRANGE questions to brothers Bill and Rich at strangetrue@compuserve.com