Scientists Invent Machine To Discover How Brain Works

THE brain, perhaps the most mystifying organ of the human body, can now be scientifically studied by a new apparatus which photographs amplified “action currents.” Invented by Dr. H. H. Jasper and Dr. L. Carmichael of Brown University, the new machine will permit physicians to study the action of the brain just as the electrocardiograph permits a revealing study of heart action.

A headpiece on the head of the patient picks up electric currents of about one ten-millionths of a volt which flow from the brain in waves, at a rate of from eight to fifty per second. The currents are carried to an amplifying box where they are intensified 500,000 times and flashed across a glass disc. The ordinary currents are smooth and wavy; when the mind is disturbed, they are sharp and irregular.

Bullets from Same Gun Linked By Camera

PHOTOGRAPHIC evidence as to whether or not two bullets were fired from same gun is irrefutably supplied by a new comparison camera invented by Dr. J. H. Mathews, University of Wisconsin professor and criminologist.

The camera marks a sensational advance of science in the war against crime. By taking pictures of opposite sections of the two bullets being checked, the camera reconstructs a composite bullet of the two sections. The resulting photographic reproduction is enlarged between 64 and 256 times the size of the bullets, permitting positive identification before a courtroom jury.

The camera is really two cameras merging into one at the single plate holder. The bottom camera takes a photo of the base of one bullet while the upper camera registers the top section of the second bullet, the two halves appearing on the print as one.

Bike Pedal Light Warns Motorists

COLORED reflectors designed for mounting on bicycle pedals were recently introduced in England as part of a “safety first for cyclists” movement.

The colored glass crystals, being continually in motion as the cyclist pedals along, glow brilliantly when in headlight beams of approaching cars.

Berlin Installs First Stamp Vending Machine

BERLIN postal authorities have adopted a new invention that promises to be of real help to all. The automatic stamp vending machine which can be attached to trolley wire posts will relieve a long felt need. The photograph shows a customer operating the crank that produces the stamps. How many times have letters been written, only to be carried in the pocket because there was no stamp with which to post it! The Berlin idea is very simple. They plan to place a vending machine near every postal box in the city. The vending machine in itself is not new, but this application is novel. The machine is simple in construction. The stamps are manufactured on rolls by the printing house. These rolls fit into the machine. A magnetic coin tester unlocks the crank when a coin has been placed in the slot. The crank then turns out the number of stamps that the machine is prescribed to deliver.

American drug stores have been the principal users of the stamp vender.

NEW EYE TESTER

THIS remarkable instrument, which is in reality a battery of lenses no bigger than a cigar box, enables the optician to secure over one million combinations of lenses almost instantaneously. The London Refraction Hospital which has recently been rebuilt at a cost of $50,000, contains this machine among many others of the same type. Testing of the human eye is one of the most difficult tasks that the eye specialist encounters. Every person has different eye strengths so this machine was developed to reveal the fact that a patient’s eye deviates by as little as a quarter of a degree from its normal outlook. The patient is fitted to the machine and then the optician adjusts the various lenses until the proper lens fits each eye.

This device is practically “fool proof” and the optician is enabled to measure the eye with extreme accuracy.

NEW TRUNK RACK FOR SEDAN

AMONG the models seen in the great automobile show at Olympia, England, was a Jowett fabric sedan. This car, as seen in the photo below, is completely covered with Jowett fabric.

Instead of equipping the car with a trunk rack and trunk, the luggage space was built within the body. The panel, in the back of the body, lifts out and upward on hinges. The opening thus exposed is large enough to hold a man and not unnecessarily crowd him.

The English motor car indicates the trend of European design.

First Consumer Electronics Show

Plans for new week-long exhibit of home-entertainment equipment

THE WEEK OF JUNE 25 THROUGH 29 will be a busy one for the electronics industry. A week earlier, the annual NEW (National Electronics Week) show in Chicago will keep manufacturers of small electronic parts and components occupied showing their wares to distributors from all over the country.

Fresh (or not so fresh) from that mammoth task, the industry will move to New York into the Americana and New York Hilton hotels for the Consumer Electronics Show—the first national exhibition especially for home-entertainment electronics.

In recent years, home-entertainment manufacturers have shown electronic devices at a show in Chicago sponsored by the National Association of Music Merchants (NAMM), mainly because there was no show specifically for home-entertainment electronics. This year’s new show has been put together by the Consumer Products Division of the Electronic Industries Association (EIA). It runs in New York the same week the NAMM Show runs in Chicago.

Exhibitors had to choose between the two or face the expense of two simultaneous shows. A very few found it necessary to make both; an overwhelming number who had no stake whatever in music as such decided to show only in the Consumer Electronics Show in New York.

We talked to Jack Wayman, staff vice president of the Consumer Products Division of EIA, who is responsible for getting the Show “on the road.” He explained some of the Show plans to us recently.

The Consumer Electronics Show (CES) will be part of Consumer Electronics Week—June 23-28, 1967. The National Appliance and Radio-TV Dealers Association (NARDA) will hold its annual convention the same week. The NARDA convention starts Friday, June 23, and finishes Sunday, June 25, the first day the CES exhibits will be open.

The first day will feature an all-industry reception and banquet in the Grand Ballroom of the Waldorf-Astoria. After that, it’s down to business. In addition to the exhibits, which open at noon Sunday, the remaining three days will feature three morning seminars (8:30— 10:30 am) planned to build profits for all the dealers who attend them. They should be full of helpful ideas.

Monday—Government and industry symposium Tuesday—Audio and video tape equipment and merchandising Wednesday—Hi-fi components and merchandising We sent letters to the companies who signed up early for the Show. From those who responded we got a fairly accurate picture of what will occur at the exhibit halls in June.

We asked first their reasons for choosing this Show. Most repeated were: “It’s the only major show devoted to home-entertainment equipment” and “It’s a limited show, not open to the public but to dealers only.” Other reasons given: “Wide acceptance among other manufacturers”; “Because it will attract East Coast buyers for big chains”; “Best way to reach a large number of poten- tial dealers and distributors.”

Whatever the reasons, the Consumer Electronics Show promises to be a success. About 100 exhibitors attest to the popularity; in fact, the space was sold out long before the deadline. Practically every kind of home-entertainment device will be shown. Considering the name Consumer Electronics Show, we expected a lot of other kinds of equipment: garage-door openers, burglar alarms, and even solid-state appliances. Not so. The CES will be devoted only to home-entertainment electronics.

The list of exhibitors is extensive, but it’s on page 83 so you’ll know who you can visit at the Show.

We asked exhibitors what products they’d be displaying. Here are some they told us will be there for dealers, distributors and buyers to see: Color television sets Portable TV’s (color and b-w) Hi-fi and stereo components Console hi-fi centers Table and portable AM radios Auto radios FM radios of all kinds CB walkie-talkies (Part 15 types) Record players and changers Tape recorders Cartridge-tape machines Video tape recorders Shortwave receivers Electronic organs Many of the items will be new to the lines of the manufacturers. From all appearances, the chief aim of most exhibitors is to find additional outlets. Distributors, dealers and retailers will all be there. Many exhibitors are counting on the attendance of buyers from large department store and discount chains—the door, often, to multiple sales that can spell quick success for a new line.

As mentioned, the public won’t be admitted. One reason was summed up by an exhibitor in this way, “For the first time we have a show of our own, one in which we have time to see the people who really can sell our goods. When we were at the Music Show (NAMM) there was not enough time for the people directly concerned with our segment of the home-entertainment field. Exhibitors will have more time to spend with people who are buyers, not lookers.”

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A Breadbox-Size Navigating System

By R.F.Gallagher

WE’RE all navigators to some degree. Navigating is simply rinding your way from one place to another and knowing where you are along the way. Usually, though, we think of navigating in terms of ships and planes.

Navigating systems have come a long way since Capt. Bligh’s famous 3,600-mi. journey on the South Seas. All he needed was a sextant because all he really wanted to do was get within sight of land. He even might have considered sailing to within miles of a pile of rocks pinpoint navigation.

That kind of accuracy isn’t good enough nowadays, of course. And hasn’t been for a long time. These days navigating means landing a craft on the moon (some 238,000 mi. away) with an accuracy down to 1/2 mi. Or orbiting a craft around the planet Jupiter (almost 400 million mi. distant) with accuracy down to 1 mi.

You may think that that kind of navigating precision has not much to do with workaday types with both feet on the ground. You may be proved wrong some years down the pike. For the Air Force’s Space and Missile Systems Organization (SAMSO) is now developing Navstar, a space-based radio navigation system—global in scope—that could provide precise navigation information by the late 1980s for users throughout the world. (A lightweight backpack model— which could be called breadbox size—has been built and is currently being tested for use by ground troops.)

The Global Positioning System (GPS) is a Dept. of Defense project, but the Air Force, Army, Navy and Marines, plus the Defense Mapping Agency, are involved. SAMSO is head honcho, or program manager.

Right now, there are four satellites orbiting the earth, the last of which was launched last December. All have been put up there by the famous Atlas family of rockets. When the project becomes fully operational, possibly in the late 1980s, the Navstar system will include 24 satellites, eight in each of three orbits. This truly artificial galaxy will circle the globe every 24 hrs., all the while beaming continuous navigation signals to earth.

SAMSO is currently working with the Federal Aviation Agency to determine the practicality and long-range use of the Navstar system in aircraft crash avoidance. Present aircraft applications are in strategic defense, with Navstar affording an all-weather, day or night global strike capability.

Another function of the system is to provide navigational fixes for missile and attack submarines which must broach the surface for as short a time as possible to avoid detection. The data received permits the craft to navigate through minefields and to pinpoint location relative to charted buoys, shoals and reefs.

The fully operational Navstar system works like this: All 24 satellites transmit individually coded, 30-sec. navigation messages simultaneously, beginning at the same time and in the same format.

The first 18 sec. contain celestial and clock data. The next segment of 6 sec. is reserved for additional messages. The final 6-sec. portion contains a course almanac for all satellites in the network.

Here on earth, the signals are received by user sets, which can be integrated with aircraft and ships or hand-held by land-based personnel.

The receiver locks onto signals from four favorably located satellites. It then processes the signals and, depending on the information sought, the user can determine his position to within tens of feet, velocity to within a fraction of a mile per hour and the time to within a millionth of a second. This information becomes available quickly with the push of a few buttons—no more difficult than punching numbers on a calculator.

The system consists of three major interlocking segments. The space segment (the orbiting satellites) broadcasts superaccurate position coordinates and timing information. The user segment (receivers) processes this information from the four best-located satellites to obtain accurate position and velocity components. The control segment (base stations on earth) tracks the satellites and continually updates their position coordinates.

The control segment consists of a Master Control Station located at Fortuna Air Force Station in North Dakota (construction is expected to begin in 1980), plus four monitor stations—in Alaska, Guam, Hawaii and at Vandenberg AFB, Calif. The monitor stations pick up signals from satellites and transmit them to the Master Control Station. These signals are used to determine and correct the errors of each satellite. The corrections are then relayed to the satellites by the Master Control Station.

The satellite itself weighs 1,673 lbs. and measures just 17-1/2 ft. from tip to tip. And, of course, its more than 33,000 parts are a wonderment of sophisticated engineering. For example, the atomic clocks used are so accurate that they gain or lose only 1 sec. in 30,000 yrs.!

The Navstar Global Positioning System, as we hinted, is a little premature for civilian use. But near-future applications involving air, sea and land vehicles abound. They include aircraft runway approaches, photomapping, geodetic surveys, aerial rendezvous and refueling, air traffic control and search & rescue operations.

Further ahead, perhaps commercial fishermen, private-plane pilots, surveyors and offshore oil-drilling outfits might plug in.

Proposed $60,000,000 Bridge Over Narrows to be Longest in World

A BRIDGE, which is to be the longest in the world, with a central span that will be 1000 feet longer than the Hudson river bridge, and towers that will be higher than the Woolworth building, is soon to be built over the Narrows between Staten Island and Long Island. The complete structure, shown in the architect’s drawing below, will have observation galleries, beacon lights, and a carillon of bells.

James Liddy’s Bedsprings

By Alfred Lief

ONE day in 1853 James E. Liddy, a carriage maker’s blacksmith, drove his wife into Watertown, N. Y., in their buggy. They were newlyweds. Young Liddy was rather irked, waiting in the seat so long. He fidgeted and bounced on the coil-spring cushion seat—then suddenly his expression changed.

He thought how comfortable it would be to sleep on springs. He would get rid of those cross ropes that were tied to his bed frame as a support for the straw and feather ticks and use cushion coil.

Liddy took measurements and sawed six slats the length of his bed. In the carriage shop he fastened six open coils to each slat, spacing them for even distribution of weight. Here it was; the first bedspring. Mr. and Mrs. Liddy—if not George Washington—slept there.

Before James Liddy went to his eternal rest in 1921 at 93, many improvements had been made and a new industry organized. Production had passed from carriage makers to mattress manufacturers. So-called bed-bottoms appeared on the market with resilient lengthwise slats on top of crosswise rows of coils; others with a woven wire net enclosing the coils; still others with double decks of coils.

According to the latest census figures, the annual volume of U. S. sales for bed-springs totals $103,664,000 wholesale. This means in 1951 more than 3,000,000 box springs were sold, more than 2,000,000 coil springs and 500,000 flat springs.

Liddy never patented his idea nor is there any evidence that he undertook manufacturing but the National Association of Bedding Manufacturers is very grateful to him. Its president journeyed to Water-town for a centennial celebration this year and gave the county historical society a miniature model of Liddy’s creation. The brass plate attached to it bespeaks James E. Liddy’s “great contribution to better rest.” His fame is secure because he benefited mankind. He, too, can rest easy. *

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Jap Pilots Ride to DEATH on Flying Bombs

By Ray Holt

The current conflict between Japan and China has brought out an amazing revelation of the methods by which Japanese pilots assure air bombs reaching their target by putting a man inside to steer them. Why? Read the reasons in this article, and you’ll have a better understanding of Japanese psychology toward the machines of war.

IMAGINE yourself strapped within a hollow chamber inside a huge air bomb, surrounded on all sides by high explosives. In front of you is an airplane type rudder which steers the tail unit of the bomb. Windows in the nose enable you to see ahead. You’re loaded into the bomb, which is placed in its nest under the fuselage of a bombing plane. The bomber takes off, soars above a target—say, an ammunition dump of the enemy. Up above you, the pilot of the plane pulls a lever.

Down you go, plunging toward the ground with terrific speed. You see that you aren’t going to strike the ammunition dump, but will land many yards to one side of it. So you twist the control rudder, swerving the bomb’s course. Success! The dump looms up directly below the windows of your bomb. And that is practically the end of things for you.

Sounds like the superheated imagining of a Jules Verne, doesn’t it—the sort of absurdity that a sensible man would laugh off as being unheard of, an astounding, amusing impossibility?

It’s nothing of the sort. It’s an actual fact of warfare, a method used by Japanese pilots who deem it an honor transcending all others to ride to glory for the mother country. They know that their memory and their families will be forever honored in their homeland.

Rumors of the flying bomb death ride have filtered out of the conflict now being waged by the Japanese and Chinese. Necessarily this information has been of a confidential, undercover nature, but not long ago it was given nation-wide publicity by a radio commentator on international affairs.

Japanese and Machines To make the man-steered bomb a credible actuality, an understanding of the peculiarities of the Japanese character is necessary. And some such understanding may sooner or later be forced upon, the great powers of the world who are all too likely to become involved in the aggression of Japanese militarists in China, where the United States, Great Britain, France, Italy and Germany do much business.

In the field of machinery the Japanese mind is at a peculiar disadvantage. They 1 are able to turn out an exact copy of any mechanism that comes into their hands, but the type of mechanical imagination which went into its original creation—which, for want of a better term, is sometimes known as Yankee ingenuity—they are at a loss to duplicate.

The simple truth of the matter is that -a man is practically required to steer Japanese bombs to their mark because they haven’t been able to develop the bomb-sighting machinery which makes Uncle Sam’s flyers, for instance, so deadly in their accuracy.

Peculiar Oriental Psychology As to why Japanese soldiers fight among themselves for the honor of being the bomb pilot who can look forward to being blown to certain oblivion, that’s a matter of psychology not so easy to understand. Patriotism rules the Japanese to an almost fanatical degree, and love of country is so bound up with religion—the emperor being regarded as an incarnate god—that to be blown up in a bomb to further the successes of Nippon becomes something to be desired above all things.

When one understands the popularity that hara-kiri, a form of suicide by self-disembowelment, has had among the Japanese for centuries, the national willingness to dive to death in a bomb, or in any other way, becomes credible.

Hara-kiri, as formerly practiced, was compulsory upon a noble of the higher class Who received a courteously phrased message from the mikado intimating that he must die for some offense of lawbreaking or disloyalty. The suicide, using a jeweled dagger customarily sent by the mikado for performing the act, proceeded in a prescribed ritual. Seated on a dais, surrounded by officials and friends, the suicide plunged the dagger into his stomach below the waist on the left side, drew it slowly across to the right, and turning it, gave a slight cut upward.

This compulsory suicide has been abolished, but the idea has such a striking appeal for the Japanese imagination that some 1500 hara-kiris take place annually as a purely voluntary gesture.

In the final analysis, the amazing thing is not that the Japanese should succeed in finding pilots for their man-bombs, for volunteers for such a mission of certain death can be found in any army in the world, but that such a weapon should be necessary. It simmers down to the fact, as hinted at above, that the Nipponese are conscious of their inferiority in developing new and fearful weapons of war, and are forced to rely on man-power.

A country like the United States would approach the problem of directing bomb flight in an entirely different way. Some method of mechanical control of the bomb would be sought—in fact, the idea of controlling a bomb or gun shell by radio is already being worked on, as described in Modern Mechanix and Inventions some months ago. It will be seen that, entirely aside from making the sacrifice of a man’s life unnecessary, radio control of a bomb is much more accurate and less liable to error through the failure of the human machine in a moment of critical nervous tension.

Superiority of American engineering brains over the Oriental variety is well demonstrated in the newest United States army bombing plane, a photograph of which is reproduced in these pages. It is a monoplane of all-metal construction—no wood or fabric to catch fire from incendiary bullets of the enemy—and is so well streamlined, with its landing gear pulled up under its belly, that it can do a top speed of 200 miles an hour, fully loaded with a two ton cargo of bombs. This is 80 miles an hour better than the speed of the Curtiss bomber, a biplane, previously used by the air corps.

Features of U. S. Bomber A revolving turret to protect the gunner in the nose of the ship is another feature. It diverts the rush of air and makes accurate aiming much easier. At high speeds, the windstream is so powerful that, in an ordinary ship, it has a tendency to wrench a swivel mounted gun out of the gunner’s control.

In connection with the possible need of protecting our country from Pacific aggression, the news that a government expedition has just left for an extensive survey of the Aleutian islands (which constitute the tip of the Alaskan peninsula) is important. A map, reproduced herewith, shows the extremely important location of these islands in their relation to Japan and the Orient.

Geologically, these islands are thought to be the sunken peaks of land that once connected the mainland with Asia. Siberia is but a stone’s throw distant, and the northern islands of Japan not much farther away. Since, by a recent bill passed in Congress, the United States has relinquished control of the Philippine islands, we will have no Pacific base of importance other than Hawaii and Guam, which makes the Aleutian chain all the more important in the scheme of national protection.

Strategic Importance of Islands Airplanes are being carried by the expedition and these will make a careful aerial survey of the islands. A weather observation station will probably be established on Tanago or Adak island, and the best suited of the nearby islands will be chosen as a possible base for an airplane field. Harbor facilities will be carefully charted with a view to possible installation of a naval base for ships and submarines. Alaska, of course, is a United States possession which we are free to fortify as we may see fit. An incident of the World War which has just come to light illustrates the ingenuity of the western mind in the world of machines. German engineers designed a mine fitted with clockwork which permitted the device to float in toward English shores when the tide was right. When the tide ebbed, the mine automatically sank to the bottom, where it waited the proper interval and then released itself again to float closer to the shore. The British were unable to figure out how the mines got there.

No Noise From Electric Rifle

NEW Army recruits suffer badly from nerves after their first session or two on the rifle range; headaches also result from noise and powder fumes. So a rifle instructor has invented an electric rifle, noiseless, powderless, harmless, since it shoots a spot of light instead of a bullet. A luminous target is first projected on the target board. When the electric gun trigger is pressed, a black spot appears on the target at the point where the gun is aimed. An ingenious system of lenses within the barrel, with an electric light bulb as projector, constitutes the mechanism of the rifle.

Thomas Foster’s School By Mail

By Alfred Lief

COAL mine accidents in the 1880’s prompted a Pennsylvania editor, Thomas Jefferson Foster, to crusade for safety laws. In his paper he ran question -and-answer columns for miners which proved so popular he later compiled them into a free handbook. But it seemed to him that the message he had to tell should be conveyed to his readers in a more systematic way.

He prepared a textbook of clear and simple instruction papers which they could study at home and added questions to be answered by mail and later corrected by competent instructors.

The Complete Coal Mining Course, as he called it, was ready in 1891. Within seven months Foster had enrolled 500 students. About 10 per cent finished and qualified as mine superintendents, inspectors and engineers. By the end of the year the enrollment was 1,200. The success of his idea proved to him that he could teach all engineering trades and professions similarly. By 1898 his International Correspondence Schools, 17 in number, had attracted 70,000 home-study students.

With each change in the industrial scene the schools met new challenges and trained new personnel. More textbooks, more courses, a larger faculty—but the system remained the same.

Thomas Foster died at 93, happy in the knowledge that many people who attained eminence had gotten their start by learning by mail—a cowpuncher had become an electrician, a ferryman a surveyor, a mule-driver a plant superintendent. This year the ICS enrolled their 6,000,000th student. •

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LIGHT THAT BENDS
AN AMAZING new optical instrument now being developed at the Imperial College of Science at London, England, is the Fibrescope. When completed, this device will enable doctors to search inside the human body, physicists to watch radioactive material from the other side of lead walls and engineers to examine hidden parts of complicated machinery.

The Fibrescope consists of a bundle of glass fibres, each one several times finer than a human hair. Looking along the axis of the bundle, an image at the other end is clearly seen, no matter how many times the bundle has been knotted, twisted or bent around corners. The instrument is expected to substitute for many of the expensive existing optical systems whose complicated arrangement of lenses makes it difficult for them to be used where flexibility is required. Drs. H. H. Hopkins and Punjabi Narinder Singh Kapany are developing the Fibrescope.

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CUSTOM CARS and HOT RODS

JUDGE a man by the company he keeps” is a proverb which has managed to survive the years. But nowadays you can substitute “the car he keeps” and still be on the right track.

For more and more motorists are getting bored with the production-line beauty and middle-class standard performance of our stock cars. And more and more of them— are actually doing something about it.

What are they doing? Well, the next time you take a spin down Lincoln Highway, take a good look at the cars that whiz by. You’ll be startled to realize the high percentage of unusual vehicles. For America’s auto enthusiasts are buying and building custom cars and hot rods as never before.

These special jobs reflect not only the individuality of their owners but the basic individuality of America. • Lon Hurley built this $8,000 dream car in eight months. Hood, grille and fenders are Cadillac parts while rear deck and doors are original design.

This Packard model never got past the experimental stage. Built to make over 125 mph. it represents an investment of more than $200,000.

Small German auto which looks like a racing car is called the Porsche. It has a four-cylinder engine in the rear of the two-seater coupe body.

Built in 1939. this French custom car has a body designed by Figoni & Falaschi and a Delahaye V-12 chassis. Owner says it can make over 115 mph.

This 17-year-old double-cowl Duesenberg phaeton is a supercharged show model with a body which was specially built by Brunn of Buffalo, N. Y. It was later listed and sold as a 1934 model.

One of the classic cars of the 1930’s, this Auburn super-charged speedster can make over 100 mph —and there’s a plaque on dashboard to prove it.

Recent motor show in Paris displayed this Super-leggera Ferrari, a long nosed Italian car. It’s only a two-seater although it has a sports coupe body.

J. S. Inskip of New York lust built this Rolls-Royce Silver Wraith (late model) for Tommy Manville and wife, shown with him. Price tag was $22,500.

Le Baron of Detroit built the body of this Chrysler Newport in 1939. It has a wide separation between the front and the back seat and sold for $25,000.

This beauty, built as a gag by Noble Heuter, has made 112 mph. It’s a 1929 Model A Ford body with roof chopped off and rear fender retained for laughs.

Evans special, a Class C Lakester, placed second recently in the Bonneville National Speed trials. The little belly-tank hot rod made 174.75 mph.

Bob Pierson’s chopped off ‘34 Ford coupe with a ‘46 Mercury engine is probably the fastest coupe in the world. It holds Bonneville record of 142.98 mph.

Only the top was built to order on Les Callahan’s ‘22 Dodge body set on a ‘32 Ford frame. The car has regular Ford axles and a ‘46 Mercury engine.

Ant Eater, which has been called the world’s faster roadster, was clocked at 152.54 mph. The entire body swings up on hinges to expose the engine and cockpit, below right. Belly-tank nose seats the driver, below left, while the 268 cubic inch modified Mercury power plant is located in the rear.

Three-quarter midget car built by Bob Feuerhelm has an all-plastic body and a motorcycle J.A.P. 30.50 cubic-inch rear engine, seen at left. Association which regulates three-quarter midget races specifies that all entrants must agree to sell cars for $2,000 in order to keep investment down.

Carash Custom is a ‘36 Plymouth with a Ford rear and a modified ‘32 Cadillac V-16 motor. It’s handmade from sheet steel over tubular framework.

Yellow racer built by Fred Ige has a ‘25 Model T Ford body and frame, a ‘28 Hudson axle and a ‘41 Mercury motor, shown at left. The car is all hand-made with aluminum shell and grille, full belly pan, bucket seat upholstered in plastic, louvered hood, Ross steering wheel and safety hubs on the wheels.

Screwdriver, a hand built streamliner owned by Bob Arner of Culver City, Calif., has had many motors in it—now a ‘45 Mercury. It’s done 139 mph.

Designed by American Gl Pat Leighton in a Jap prison camp, this ‘32 Ford channeled roadster with a ‘42 Mercury engine has made 117.64 mph.

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Meet Hans Krause

His pocket-size sculptures are soothing to handle, sweet-scented and habit-forming.

ONE PATH to serenity, say the Buddhists, is through contemplating certain objects: the sky, a tree, a design. Not relying on sight alone, the Chinese have long used hand stones—small objects combining form and smoothness in a way that makes them delicious to handle.

Hans Krause, a German sculptor living in the Mediterranean island of Ibiza, has revived the hand stone. Playing with his dactylforms (Greek daktylos means finger) not only replaces habits like smoking but can produce calmness even in extremely disturbed mental patients. While admitting their value as medicine, sculptor Krause insists that his pocket sculptures are primarily works of art. Each is an individual form in polished Savina wood, a rare Mediterranean material that takes a thousand years to grow and yields an aromatic scent when warmed in the hand.

Kiddie Car-Belt

RICHARD G. OSTRANDER of Yonkers, N. Y. is not a man who puts things off till tomorrow!

Recently his young son narrowly escaped injury when he was thrown off an automobile seat by a sudden stop. To Ostrander this was a situation when stop meant go. He decided to do something about it and a few days later he presented to harassed parents everywhere his Wiggly Car Belt, a safety device for youngsters.

The belt, which can be installed in a few seconds, is made of sturdy webbing and consists of two sections. One encircles the back of the car seat and the other fits around the child’s waist. The latter slides up and down the back strap by means of a D-ring. This arrangement allows the child to stand, sit or lie down as he desires but prevents him from falling from the seat or being thrown into the dashboard or windshield when the car stops suddenly. The Wiggly Belt can be left permanently attached to the seat. Junior, too, if you wish.

Blind Can Now Read Printed BOOKS

ORDINARY printed books can now be read by the blind, thanks to the genius of M. Thomas, a French inventor, whose remarkable device is illustrated on this page, photo-electric cells, which, as is well-known, are sensitive to light, hold the secret of the machine’s operation.

The book to be read is placed on a moving carriage beneath a lens, and the page is illuminated by a powerful lamp. Suppose that the word being read contains the letter “R,” which is used as an example in the accompanying drawings.

How the Letters Are Read

Light rays pass from the “R” through a lens and are thrown upon a mirror which in turn projects the rays onto a panel of 42 photo-electric cells, arranged like a checkerboard. Certain of the cells, it will thus be seen, are thereby darkened by the shadow of the letter. All that remains, therefore, to convert this shadow into something which can be read by a blind person, is to make the cells register themselves in tangible, “touchable” form.

This is accomplished by having each cell operate an electric circuit comprising an electro-magnet with suitable relays. A touch-plate, corresponding to the checkerboard of 42 photo-electric cells, is perforated with 42 holes in the same arrangement, and through each hole runs a small metal rod, in much the same way as a piston in a cylinder.

To get back to our letter “R,” the particular photo-electric cells which have been darkened by the shadow of the letter actuate an electric current which sets the electro-magnets into action and results in certain of the metal rods being forced up through the perforations of the touch plate.

The rods thus raised will be the ones corresponding to the cells darkened by the projected shadow of the letter being read, and the blind reader is thus enabled to identify the letter “R” by feeling it take shape under his fingers.

The next step is to move the book on to the next letter in the word. A hand operated crank accomplishes this result. Each letter is read in turn until the book is completed.

If this explanation of the operation of the device sounds complicated, a glance at the drawing below will show that its principle is really quite simple.

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William Gray’s Pay Telephone

By Alfred Lief

THE young wife of a machinist in Hartford, Conn., fell critically ill. The year was 1888. There were few telephones in town and William Gray had to call a doctor. He ran to a nearby factory and asked permission to use their phone. The manager said no; it was not for public use. But his pleading won consent, the doctor arrived in time and Mrs. Gray survived.

William Gray’s mind clicked with an idea. Pay telephones did not exist in those early years of Alexander Graham Bell’s invention. Gray saw a need. He proceeded to find a way.

His first thought was a box covering up the mouthpiece. On the principle of the slot machine, the box could slide open and

give the caller access to the telephone. But the telephone company officials who examined Gray’s device shook their heads. The thing was impractical. It let a person make any number of calls on one nickel. It did not permit a call to be made to another pay station unless the person called also deposited a coin to unlock that instrument. No means was provided for returning the coins if calls didn’t go through.

After tackling many theories Gray decided that the instrument should remain open. A user would reach the operator in the usual way, then deposit money as she directed. With each drop in the slot the caller would ring a bell. The only trouble with these signals was that the operator couldn’t hear them! One day in Gray’s workroom a coin slipped out of a helper’s hand and fell on a bell. Gray was startled. Then he saw his solution. The coin itself must give the signal. The bell must be placed in its path.

In 1891 the Gray Telephone Pay Station Company was formed with Amos Whitney of Pratt & Whitney as president and Gray as general superintendent. They manufactured the instruments and set them up on posts (like street-corner fire alarm boxes), in cabinets (resembling grandfather clocks) and as desks.

Today the pay station is commonplace— 945,000 of them in the United States. Indispensable? Worth everybody’s while? They take in more than 9,000,000 calls every day.

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A PORTABLE COLOR RECORDER

Newest type of helical-scan video tape machine has been colorized

By JOE ROIZEN*

RECORDING COLOR TELEVISION SIGNALS on magnetic tape has been practical since 1958 when the first compatible color broadcast recorders went into service. These transverse studio machines use four heads which rotate at right angles to tape travel (see Fig. 1). The machines also contain very complex circuitry and time-base correction devices. The circuits are necessary to achieve studio-quality NTSC playbacks that meet FCC specifications for on-the-air transmission; such VTR’s (video tape recorders) range in price from $40,000 to $100,000.

The development of inexpensive helical videotape recorders (Fig. 2) for monochrome industrial and home applications, coupled with the current color boom, has led to investigations into relatively simple, inexpensive ways to colorize these recorders. The pilot-carrier principle has proved a suitable system. Modifications to a normal monochrome recorder (Ampex VR-7000) and a home color receiver make it possible to record and play back color programs with a fidelity approximately equal to off-air home reception.

The time-base problem The NTSC color signal is composed of interleaved monochrome and chrominance signals amplitude-modulated on an rf carrier. The monochrome portion of the video signal requires only that the horizontal sync coming from tape have less than a 0.15% per sec2 rate change for stable monitor images. This is a fairly large and easy-to-meet requirement for modern videotape recorders with head-drum servos. The chrominance portion, however, has a subcarrier signal of approximately 3.58 MHz. The instantaneous phase of this subcarrier determines hue in the reproduced image. One cycle of the subcarrier (360°) has a 0.279-usec period, and a 10° error in subcarrier phase will produce a noticeable hue shift. 10° represents only about 8 nsec. Allowing for the accumulation of record and playback errors, a time base of better than 4 nsec is needed to reproduce faithful color pictures. Such an extremely fine time base is not easy to attain.

Any rotating mechanism is subject to undesirable movement due to mechanical and electrical eccentricities, dynamic imbalance, walking bearings, etc. The head-drum assembly in a VTR will normally display such variations in angular velocity as a time-base displacement of the reproduced signal. A monochrome picture may exhibit slight jitter, which is usually masked by the flywheel effect of the horizontal sync circuit of the home receiver. But when color is added, the rotating-head displacements show up as constant changes in subcarrier phase and the image looks as though it has lost color synchronization.

The pilot-carrier principle The composite color signal used for recording in the VR-7000-A (the color version of the VR-7000) is also fed to a burst separator which phase-locks a crystal oscillator running at the color subcarrier frequency (see Fig. 3). The output of the crystal oscillator is divided by 7 in a tuned circuit that yields 511 kHz, as shown in Fig. 4. The 511 kHz is then multiplexed at a 5% level onto the FM signal applied to the recording head. The current through the head then has a 5% pilot-carrier content. The level must be high enough to be detectable in the playback circuits yet low enough to minimize interference visibility in the reproduced image.

In playback (Fig. 5) the 511-kHz signal is recovered at the head preamp output, and a bandpass filter isolates it from the FM signal carrying the video information. Two limiters amplify and clip the signal to a uniform level; the pulses now drive a Schmitt trigger whose square-wave output goes to a second bandpass filter centered at 3.58 MHz, the 7th harmonic of the 511-kHz pilot carrier. The 3.58 MHz is amplified and fed out of the recorder to the chrominance demodulation circuits of the modified home receiver. The set’s own quadrature circuits form the 0° and 90° signals to decode the color information.

Since the pilot-carrier signal is subject to the same time-base displacement errors that the composite video signal is experiencing, the time relationship be- tween the pilot carrier and the desired signal remains constant. Hence the color signal can be decoded with reasonable time-base accuracy. The local oscillator in the color receiver is temporarily deactivated during VTR playback.

Recorder operation The signal system of the VR-7000-A (Fig. 6) must be capable of handling a bandwidth of at least 4.2 MHz to not attenuate the color sidebands. To eliminate unwanted noise, spurious high-frequency signals, etc., the input is filtered by a phase-linear 4.5-MHz low-pass filter network.

A fast-switching multivibrator-type modulator converts the video signal to FM. The carrier and deviation frequencies are somewhat elevated from their monochrome counterparts to minimize intermodulation effects between the FM signals and the high-energy color sub-carrier (Fig. 7). The modulator operates between 5.5 MHz at sync tip to 6.6 MHz at peak white. A rising pre-emphasis going up to 14 dB at the color sub-carrier improves signal-to-noise ratio and differential gain and phase. The FM signal goes to a head-driver amplifier which provides a constant-current source to the recording head up to 15 MHz. A rotating transformer with an 8-to-l ratio transfers the amplifier output to the transducer. A 50-microinch head gap is employed.

In playback (Fig. a low-impedance preamp gives a flat frequency response. Aperture correction and equalization are applied to the FM signal before 50 dB of shunt limiters eliminate variations in signal amplitudes.

The output of the limiter is a constant-amplitude FM signal. A pulse-count detector and a 4.2-MHz phase-linear low-pass filter convert the signal back to video and remove residual carrier and deviation components. The output amplifier feeds two 75-ohm outputs, and the monitor (receiver) must be “jeeped” (rf and i.f. stages bypassed) to provide direct access to the video circuits.

Further development of a heterodyne signal-processing system will eliminate the need for modifying the home receiver. At that time it will be possible to modulate the composite video signal on a carrier and feed it into the set through the antenna terminals on an unused channel.

A color-kill circuit in the VR-7000-A detects the presence of bursts on the input signal and activates the pilot carrier in the record mode. If no burst is present, the pilot carrier is shut off so that the recording will not contain the 511-kHz signal. Under certain background conditions, faint vertical lines can be seen in the playback image due to interference from the pilot carrier. The level, however, is not high enough to be objectionable and with normal image conditions, is not noticeable.

The colorized VR-7000-A produces acceptable color pictures for most non-broadcast uses, such as educational, industrial and home applications.

Radio Equipment for Autos Brings Broadcast Programs to Motorists

RADIO, it seems, is destined to be installed in everything that flies, runs on wheels, or floats on water. The fast moving auto is the latest vehicle to be invaded by radio’s onward march.

Equipment has recently been placed on the market for installation in automobiles. As shown in the photo below, the control dials are installed on the dashboard, while the apparatus occupies a small space up under the cowl. The location of the loud speaker is optional, the space under the cowl being preferable. The antenna is ordinarily strung up in the roof, but many cars are equipped with built-in and invisible antennas, especially in the de luxe models of expensive makes.

Brain Waves Are Measured with Radio Amplifier

With an ordinary radio set for an amplifier, a young scientist at London is measuring brain waves. A fairly regular electrical wave emanates from the human brain during normal thought, but the waves diminish during sleep. The intensity of the waves is measured on an electric meter, enabling research men to study the relative intensity of thought processes.

Plastic Football Helmets. Only half as heavy as the familiar leather-and-fiber helmets, these headgear are weather resistant and have as much or more protective strength. Made by MacGregor-Gold-smith, of Cincinnati, they are molded in one unit from phenolic laminated material.

Pushbuttons replace dials on telephone

Tests in regular service last winter at Carnegie and Greensburg, Pa., suburbs of Pittsburgh, have shown it’s easier and more than twice as fast to press buttons for a phone call than it is to twirl a dial. As each “touch-tone” button is pushed, it sounds a pleasing musical tone.

Bell is introducing the phone area by area, will nave it in general use within the next 10 years.

Outboard Starter Rewinds Itself

A NEW starter for outboard motors makes obsolete the rope starter heretofore used. A steel tape, which automatically winds itself into the container in readiness for the next pull as soon as it is released is the feature of this device.

Boating enthusiasts who have had difficulty in finding their starting ropes—who have lost their ropes upon the sudden kick-back of a motor—whose wives have protested when the knot of a suddenly released rope snapped back over their heads—who resented picking up grimy, oil-soaked ropes—who have wasted time winding the rope around the starting plate—all have hailed this development as the greatest boon to outboard motoring since the development of the tilting propeller years ago.

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Public Key Cryptography

An introduction to a powerful cryptographic system for use on microcomputers.

John Smith
21505 Evalyn Ave.
Torrance, CA 90503

Cryptography, the art of concealing the meaning of messages, has been practiced for at least 3000 years. In the past few centuries, it has become an indispensable tool in the military affairs, diplomacy, and commerce of most major nations. During that time there have been many innovations, and cryptography has changed and grown to accommodate the increasingly complex needs of its users. Present techniques are very sophisticated and provide excellent message protection. Current developments in computer technology and information theory, however, are on the verge of revolutionizing cryptography. New kinds of cryptographic systems are emerging that have incredible properties, which appear to eliminate completely some problems that have plagued cryptography users for centuries. One of these new systems is public key cryptography.

In public key systems, as in most forms of cryptography, a piece of information called a key is used to transform a message into cryptic form. In conventional cryptography this key must be kept secret, for it can also be used to decrypt the message. In public key cryptography, however, a message remains secure even if its encryption key is publicly revealed. This unique feature gives public key systems great advantages over conventional systems.

This article deals with the theory and application of public key cryptography. It reviews the methods and problems of traditional cryptography and describes the remarkable concept and advantages of public keys. It also describes a real public key cryptosystem, showing examples of the encryption and decryption operations; and it attempts to clarify the concept of trap-door one-way functions, upon which public key systems are based.

Computers are essential for implementing many modern cryptosystems, including the one described here. Several BASIC-language programs (TRS-80) are included to illustrate algorithms used in this system. These can be used to experiment with the encryption, decryption, and derivation of small keys.

Conventional Cryptosystems.

A cryptosystem must have two methods for transforming messages: a method of encryption, which renders messages unintelligible; and a method of decryption, for restoring them to their original forms. For simplicity, normal message text shall be called plaintext, and the encrypted form, ciphertext. Ciphertext messages may also be called cryptograms, or may just be called messages when it is clear that the encrypted form is meant.

To appreciate the significance of a public key system, we need to know some of the methods and problems of conventional cryptosystems. In a conventional system (see figure 1), a plaintext message is converted to a cryptogram by an encryptor and sent over a communication channel. While in transit, the cryptogram may be intercepted by someone other than the intended recipient. If it is encrypted well, it will be meaningless to the interceptor. At the receiving end, the cryptogram is converted back into plaintext by a decryptor. The encryptor and decryptor may be procedures executed by people or computers or may be specially constructed devices. In any case, they are both supplied with keys from a key source.

Cryptographic keys are analogous to the house and car keys we carry in our daily lives and serve a similar purpose. In many modern systems, each key is a string of digits. For example, keys defined by the Data Encryption Standard of the National Bureau of Standards consist of 64 binary digits, 56 of which are significant. To encrypt a message, a key and the message are somehow inserted into an encryptor, and the cryptogram that emerges is a jumble of characters that depends on both the message and the key. To decrypt the message, the correct key and the cryptogram are inserted into a decryptor, and the plaintext message emerges. In conventional systems, the correct key for decrypting a message is the same one used to encrypt it. Obviously, the keys used must be closely guarded secrets.

In a good system the number of possible keys should be very large, and decryption of any cryptogram should be possible with only very few of the keys, often with only one. These conditions make it impractical to try decrypting a message with one key after another until the one that reveals plaintext is found. The Data Encryption Standard provides more than 7 X 1016 keys (a 7 followed by 16 zeros), and there is some controversy over whether this number is sufficient!

The keys to be used are obtained from a key source, which selects them, perhaps randomly, from the large set of all usable keys. The key source may be located near the encryptor, near the decryptor, or elsewhere. But each key to be used must be made available to both the encryptor and the decryptor. Therein lies the most serious problem of conventional cryptosystems: some safe method must exist for distributing secret keys to the encryptor and the decryptor.

This problem is illustrated with a simple example: let’s say you want to communicate privately with a friend named Mary. Many communication channels are available to you, none of which may be completely private: telephone, mail, and computer networks, for examples. You could send encrypted messages, but Mary could not read them without the keys. And you dare not send secret keys over these public channels. One of you must visit the other, so that you could agree on a key to use for future correspondence. But if your communication need was for only one private message exchange, it could be transacted during the visit, rendering the conventional cryptosystem unnecessary. Or if your communication need were immediate, a personal visit could cause an unacceptable delay. And if you need to communicate with several people, all the necessary visits could entail considerable expense.

Most conventional cryptosystems, including the Data Encryption Standard system, have this problem. Public key cryptosystems, however, can avoid this problem entirely.

Public Key Systems.

The concept of public keys may be one of the most significant cryptographic ideas of all time. A public key system has two kinds of keys: encryption keys and decryption keys. It may seem that having two kinds would make the key distribution problem worse, or at least no better. These keys, however, have remarkable, almost magical, properties:

• for each encryption key there is a decryption key, which is not the same as the encryption key
• it is feasible to compute a pair of keys, consisting of an encryption key and a corresponding decryption key
• it is not feasible to compute the decryption key from knowledge of the encryption key

Because of these properties, Mary and you can use a public key system to communicate privately without transmitting any secret keys. To set it up, you generate a pair of keys, and send the encryption key to Mary by any convenient means. It need not be kept secret. It can only encrypt messages—not decrypt them. Revealing it discloses nothing useful about the decryption key. Mary can use it to encrypt messages and send them to you. No one but you, however, can decrypt the messages (not even Mary!), as long as you do not reveal the decryption key. Figure 2 illustrates the flow of information in this situation, with Mary on the left and you on the right. To allow you to send private messages to her, Mary must similarly create a pair of keys, and send her encryption key to you. You can also go a step further. Since your encryption key need not be kept secret, you can make it public, for example, by placing it in a computer network public file. Once you have done so, anyone who wants to send you a private message can look up your public key and use it to encrypt a message. Since you need not transmit the decryption key, and since it cannot be computed from your public key, the message is secure. Only you can decrypt it. Other people can place their encryption keys in the same public file, which would thus become a directory of public keys. Any two people with directory entries could then communicate privately, even if they had no previous contact. It would be necessary, however, to protect the keys in such a file so that no one could change someone else’s encryption key, for example, by substituting another encryption key. Fortunately, there is a way to protect the keys themselves with a public key cryptosystem, but that is another topic.

The RSA Cryptosystem.

Now that the general concepts of public key cryptography have been examined, the next problem is how to design an actual working system. Indeed, when Whitfield Diffie and Martin Hellman conceived the basic properties of this cryptosystem in 1976, no one knew how to make a system that could employ them. The situation was similar to that of space travel in 1950. It was conceivable, but no one had accomplished it. In 1977, three researchers at the Massachusetts Institute of Technology, Ron Rivest, Adi Shamir, and Len Adleman, published an elegant method for creating and using public keys.

In the Rivest-Shamir-Adleman (or RSA) cryptosystem, the keys are 200-digit numbers. The encryption key is the product of two secret prime numbers, having approximately 100 digits each, selected by the person creating the keys. The corresponding decryption key is computed from the same two prime numbers, using a nonsecret formula.

Anyone who knows the secret prime numbers can compute the decryption key, but the primes are hidden because only their product, the encryption key, is revealed. Of course, the primes may be discovered by factoring the key, but factoring such a number is about as easy as traveling to Alpha Centauri, especially if the person who constructs the number has done it in a way that discourages factoring. Rivest, Shamir, and Adleman estimated that a fast computer would require 3.8 billion years (nearly the estimated age of the earth) to factor a 200-digit key. Estimates of the time required to factor keys of several other lengths are shown in table 1.

Before encryption, a message is converted into a string of numbers. This step is common in cryptosystems, as it is in computers and communication systems. Next, the message is subdivided into blocks, much as computer text files are subdivided into records or sectors. Each block contains the same number of digits, and is treated as one large number during encryption. To encrypt the message, an arithmetic operation involving the encryption key is performed on each block, resulting in a cryptogram containing as many blocks as the original message. The arithmetic operation, described below, is the same for all blocks. To decrypt, the inverse arithmetic operation, which requires the decryption key, is performed on each block of the cryptogram. The result is the original message in its numerical form.

As you can imagine, it would be cumbersome to illustrate these operations with 200-digit numbers, so the detailed descriptions below use small keys and messages; otherwise, the operations shown are the same as those used in a full-size RSA system. Also, the encryption method described here is actually a subset of the original RSA method. This modification, which is due to Donald Knuth (see reference 3), uses the basic RSA technique, while lessening somewhat the number of computations involved. (For more detailed information, the reader should refer to the original Rivest-Shamir-Adleman paper, shown as reference 5.)

How to Encrypt.

While the encryption and decryption operations are normally performed by a computer program, I will describe them as if you were performing them by hand. Normally, the only manual operation required is entering the message to be encrypted.

Suppose you wish to encrypt the message

MARY HAD A LITTLE LAMB.

Once entered into a computer, the message will be in numerical form, frequently in ASCII (American Standard Code for Information Interchange). In ASCII, this message is

77 65 82 89 32 72 65 68 32

65 32 76 73 84 84 76 69 32 76 65 77 66 46

This is not yet encrypted, of course. It is merely written as a computer might represent it (all the numbers in this article are decimal). Group the message into blocks with six digits each:

776582 893272 656832 653276 738484 766932 766577 664600

Each block except the last consists of three consecutive characters from the ASCII representation above. The last block consists of the last two characters plus two zeros added at the right to make the final block as long as the rest. Digits added for this purpose may have any value.

Suppose that the encryption key, usually called n, is 94815109. This is the product of two prime numbers. To encrypt the message, treat each block as a number, and cube it modulo n (see the text box “Arithmetic with a Modulus”). For example, to encrypt the first block of the message:

(776582 X 776582 X 776582) mod 94815109 = 71611947

Performing the cubing operation on all eight blocks produces the cryptogram

71611947 48484364 03944704 03741778 61544362 35331577 88278091 50439554

Arithmetic modulo n is a fundamental part of the RSA system. It is also used in decryption and creating keys. Most of us have used arithmetic modulo n, although perhaps we didn’t call it that. For instance, arithmetic modulo 12 is frequently used in calculations related to keeping time. The text box “Arithmetic with a Modulus” reviews the mechanics.

Almost any method may be used to convert the text to numbers. It would have worked just as well to use A = l, B=2, . . . Z = 26, but the ASCII code is already in wide use, and it includes numbers for spaces and punctuation. The block length should be almost equal to the key length, because making it long minimizes the number of blocks per message. When considered as a number, however, no block should be as large as the key. For the above key, no block should be larger than 94815108. Making the block length slightly less than the key length ensures that this requirement is met. Of course, with full-length keys, there will be about 100 characters per block.

Listing 1 is a BASIC program that uses the above key to encrypt a line of text. Two lines of the program (670 and 680) perform the encryption. The rest deal with input, formatting, and printing. If desired, the encryption key in line 220 may be changed; use a key with seven or eight digits, or reduce the number of characters per block (line 210).

The programs in listings 1 through 4 were written for the TRS-80 BASIC interpreter, which is capable of 16-digit precision. They may be adapted for use with other interpreters, and I have tried to structure and annotate them well enough to make them easy to modify.

How to Decrypt.

Since the RSA system is a public key system, the decryption key, usually called d, differs from the public encryption key. For the above encryption key, d is 63196467. Knowing the value of d, you can decrypt the message by raising each cryptogram block to the power d, modulo n. That is, if a cryptogram block is C, you must compute (C) mod n. For example, to decrypt the first block of the above cryptogram:

(71611947^63196467) mod 94815109 = 776582

converts this block back to the first three ASCII codes of the original message. Each of the remaining blocks is decrypted in the same way. Fortunately, raising a number to a large power does not require performing a comparable number of multiplications. One efficient algorithm is a variation of the “Russian Peasant Method” of multiplication (see reference 4). It computes M = (C^d) mod n, as follows:

1. Let M = 1.

2. If d is odd, let M = (MXC) mod n.

3. Let C = (CXC) mod n.

4. Let d = integer part of d/2.

5. If d is not zero, repeat from step 2; otherwise, terminate with M as the answer.

To raise a number to the power 63196467, this algorithm executes its loop (steps 2 through 5) 26 times. It is employed as a subroutine in the BASIC-language decryption program of listing 2. Line 200 contains the keys, which may be changed, if desired. Lines 340 through 380 execute the algorithm.

How to Derive Keys.

Earlier, I said that it is feasible to derive a pair of keys, n and d, for encryption and decryption, but not feasible to calculate d from n. That seems incredible, but experts believe it is true when n and d are constructed in the following way.

The encryption key, n, is the product of two large prime numbers, p and q:

n = pq (1)

The decryption key, d, is calculated from p and q by

d = [ 2(p-l)(q-l) + 1 ]/3 (2)

Although n is made public, p and q remain secret. If n is sufficiently large, say 200 digits, it is practically impossible for anyone to factor it and discover the values of p and q; and without knowing p and q, it is equally difficult to compute d.

For the encryption and decryption examples given earlier, the keys were constructed as follows:

prime number, p = 7151 prime number, q = 13259 encryption key, n = 7151X13259

= 94815109 decryption key, d = (2X7150X 13258 + l)/3

= 63196467

Because p and q may have 100 or more digits in an operational RSA system, their selection requires computer assistance. The following three restrictions apply to how they should be chosen. First, neither p — 1 nor q — 1 must be divisible by 3, or the decryption operation will not work correctly. Second, p — 1 and q — 1 should both contain at least one large prime factor. Third, the ratio p/q should not approximate a simple fraction, e.g., 2/3, 3/4, etc., etc. These last two restrictions help ensure that n will be difficult to factor. Donald Knuth, in the second edition of his book (see reference 3), gives a detailed procedure for selecting p and q, which ensures that these restrictions are met. While the procedure described is for constructing 250-digit keys, it is applicable to other key lengths.

Enough keys are available for everyone. The number of 250-digit keys constructible with Knuth’s procedure is much greater than 10^200. For comparison, the number of atoms in the known universe is about 10^80.

To create a different pair of seven-or eight-digit keys, find primes p and q such that neither p — 1 nor q— 1 is divisible by 3, and the product n=pq is a seven- or eight-digit number. Then calculate d from formula (2). Divisibility by 3 is easily checked by casting out 3s, and the BASIC programs described below are helpful in finding prime numbers.

How to Find Large Prime Numbers.

To find a large prime number, select a random odd number of the required size and determine whether it is prime. If it is not, increase it (or decrease it) by 2 and try again, repeating until finding a prime. It is not necessary, however, to attempt to factor a number to determine whether it is prime.

To test whether a number n is prime, select any number greater than 1 and smaller than n, say x, and calculate

y = (x^n-1) mod n

If y is not equal to 1, n is not prime. But if y = 1, n may be prime, and further testing is required. Repeat the test using another value of x. If this test is performed with many different values of x, and if y = 1 for all the test cases, n is probably prime. Listing 3 is a BASIC program that uses 10 values of x to test a number for primality. If the program says the number is not prime, it is not prime. But if the program says the number is probably prime, there is a small chance that it is not.

What is the probability that this program will make an error? I don’t know, but it illustrates a class of programs, some of which are very good. Knuth (reference 3, page 375) presents one that is slightly more complicated, for which the odds against an error are a million to one when 10 values of x are used for testing, and are a million million to one when 20 values are used. For serious work I would use the more complicated program, but the one presented here illustrates the process of testing without factoring—and it doesn’t seem bad. It has not made an error in several hundred trials.

Listing 4 is a BASIC program that searches for a prime number using the same test method as the previous program. The program will begin with the number you enter and search downward until it finds a probable prime, which it will identify. If you enter 99999999, it will find the largest eight-digit prime. This program helps to find primes for constructing small keys like the ones above.

One-Way Functions and Trap-Doors.

Public key cryptosystems derive their unusual properties from mathematical functions called trap-door one-way functions, which are useful because they can act as ordinary functions or as one-way functions.

One-way functions are like oneway streets. The ordinary cube function, B = A3, resembles a one-way function in that it is easier to calculate B, given A, than it is to calculate A, given B. The latter calculation, the cube-root function, is called the inverse of the cube function. The inverse of an automobile would convert smog to gasoline. A mathematical function is said to be one-way if it is much more difficult to compute the inverse than to compute the function itself. To qualify as a one-way function, the inverse must be very difficult to compute, even by machine.

A function that could be computed in a few seconds, for which computing an inverse required thousands of years, would fit the definition.

To create a public key cryptosystem, a trap-door one-way function is used. It is easy to compute an inverse of a trap-door one-way function, but it can be very difficult to determine how. Computing an inverse can take millions of years because finding out how to do it can take that long. If the method is known, computing an inverse may take only a few seconds. This is a completely different situation than that created by a one-way function, for which there is no easy way to compute an inverse. When a trap-door one-way function is being constructed, the person constructing it has access to information, called trap-door information, that reveals how to compute inverses. Once the function is constructed, the trap-door information is hidden so well that it can take millions of years to find.

The Knuth modification of the RSA system encryption function, cubing a number modulo n, is a trapdoor one-way function. Its inverse function is the cube root modulo n. In arithmetic modulo n, “cube root” is defined as in ordinary arithmetic: if B is the cube of A, then A is the cube root of B. Notice that this definition does not say how to compute cube roots (in either kind of arithmetic). If you know how to compute cube roots modulo n, you know how to decrypt messages. In modulo n arithmetic, the cube root of B is computed by raising B to some power d, modulo n. But knowing this doesn’t help unless you know the value of d. And d can be computed by formula (2) if n has two factors (p and q), and p — 1 and q — 1 are not divisible by 3. If you construct the modulus, n, you know p and q, and can therefore calculate the value of d. Knowing d, you can compute cube roots; in other words, decrypt cryptograms. The values of p and q are hidden from other people by the difficulty of factoring n. They are deprived of the value of d, and therefore cannot compute cube roots. Hence, they cannot decrypt cryptograms created by cubing modulo n. In the RSA system, the value of d is the trap-door information that reveals how to compute inverses (cube roots). You might think of p and q as comprising a trap-door through which the value of d is obtained. Factoring n is analogous to finding the trap-door, but it is very difficult to do.

Other trap-door one-way functions undoubtedly exist, and these could be the foundations for other public key cryptosystems. For each of these systems, the same principles would apply. The creator of the system parameters would have access to certain trap-door information, which would reveal how to compute inverses. For everyone else, the trapdoor would be hidden, and for them the encryption function would be, in effect, a one-way function.

Is the RSA System Unbreakable?.

Successfully analyzing a cryptosystem, and being able to read its cryptograms without authorization, is called breaking the system. Theoretically, the RSA system can be broken by a determined analyst. Factoring the encryption key, or modulus, would do the trick, for then the decryption key could be easily calculated from formula (2), after which any message could easily be decrypted. However, factoring a key of the recommended length and construction does not seem feasible. Knuth gives a procedure for constructing a 250-digit key and considers it inconceivable at this time that such a key could be factored. Experts acknowledge that a breakthrough in the art of factoring large numbers would render the RSA system worthless but consider such a breakthrough extremely unlikely. Apparently, factoring large numbers is not a new problem, but one that expert mathematicians have attacked for centuries, and it is known to be very difficult.

Another way to break the system is to determine the value of d without factoring n. Although you can approach this problem in several ways, experts believe that none of them are likely to be fruitful.

Yet another method of breaking the system is to learn how to compute cube roots modulo n without knowing the value of d. Less seems to be known about the difficulty of doing this than is known about the difficulty of factoring n. At this time, no one knows how to compute such cube roots in a reasonable time without knowing d.

Any new cryptosystem should be viewed with suspicion. The accepted method of demonstrating the adequacy of a new system is to subject it to prolonged, concerted attack by people with experience in breaking other systems. If the new system proves resistant to such an attack, it may tentatively be considered secure. The process of validation is continuing, but a fairly large number of preliminary studies done so far indicate that the system is quite secure.

Digital Signatures.

Very closely related to public key cryptography is the concept of digital signatures. One problem with corresponding electronically, such as via a computer network, is that messages can be easily forged—you usually cannot be certain that the sender of a received message is actually the person claimed in the message. A public key cryptosystem, however, can be used to provide positive identification of any sender who has a public key on record. If, for example, Mary has filed a public key in some public access file, she can digitally sign a message to you by decrypting it with her private key before transmitting it. After receiving the message, you (or anyone else) can read the message by encrypting it with Mary’s public encryption key. The process is essentially the reverse of the cryptosystem: the message is first decrypted and then encrypted, and anyone can reveal the message, but only Mary with her secret decryption key can create it.

In addition, messages using digital signatures can be subsequently encrypted with another key. After Mary decrypts her message to you with her secret decryption key, she can then encrypt it with your public encryption key. The result is a message that only Mary could have created, and only you can read!

Messages with digital signatures have other interesting and useful properties and may be used to advantage with other (non-PKC) cryptosystems. These properties and applications might easily justify an article on digital signatures alone.

Summary.

This article has described the principles of public key cryptosystems. One example has been given, the Rivest-Shamir-Adleman system. We have seen how keys are constructed and used, and have at our disposal four BASIC programs for further experimentation. These programs may also be useful as models for assembly-language programs that could manipulate larger numbers and run faster. We have seen that the RSA cryptosystem provides public keys in more than astronomical quantities and that it is believed to be unbreakable.

Several questions come to mind: Is a personal computer powerful enough to run a full-size RSA system? How long would a small computer take to construct a 200-digit key? Or even a 100-digit key? How long would it take to decrypt a medium-length message?

Regardless of the answers to these questions, the prospects are good for using public key systems with small computers. New computer models appear almost monthly, and their performance is improving rapidly. The theoretical work that gave birth to the RSA system is also proceeding at a rapid pace, and we can expect new and different public key systems to result from that work. Some of these may be suitable, perhaps even optimized, for small machines, and the prospects are exciting.

Waterproof Sand Exhibited

W/ATERPROOF sand constituted one of the many marvels of modern chemistry exhibited at a Chemical Industries Exposition recently staged in New York, N. Y. In a convincing test demonstration, water was passed through a series of curves in the chemically treated sand without becoming even partially absorbed.

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Science Transplants Babies

BY LESTER DAVID

The embryo conceived by one mother has been removed from her womb, stored by refrigeration, then transplanted to another mother for normal birth. Mother’s name Is “Mrs. Rabbit”—some day it might be Mrs. Jones.

IF YOU could mate a man and a woman—could let the embryo get just a start, then transfer it to the body of another woman to complete its prenatal growth and be born—that would start a revolution in human genetics, wouldn’t it!

It’s just been done with rabbits.

It certainly will be done next with cattle.

And just as certainly it will some day be possible with human beings!

To a brilliant young Chinese-American, Dr. Min-Chueh Chang, an experimenter under Dr. Gregory Pincus, head of the Worcester Foundation for Experimental Biology, goes chief credit for the startling new two-mother rabbit.

Dr. Chang’s work is no laboratory curiosity. It is intensely practical. For example, it will eventually affect the size and juiciness of the steaks on our dinner tables—and the frequency with which we can have them. For beefsteaks do not come from just any kind of cattle. There are strains no good at all for beef, but which may give lots of milk. There are other strains that are fine for beef but poor for milk. Still others, scrubs, aren’t particularly good for anything.

Now, it is the chief task of breeders to produce healthy strains which give maximum amounts of a product (like beef or milk) of high quality. Working for beef, they have done much in the last hundred years, supplanting the lean, wiry, poor-for-beef Texas Long-horn with square breeds heavily upholstered with luscious meat—but the process has been slow. It takes a standard amount of time for a cow to have a calf; the process can’t be hurried. At one experiment per prize cow per year the improvement of cattle breeds proceeds at a snail’s pace.

Scientists wondered, How can the process be hurried, so that ten experiments can be made where only one is made now?

Noted experimental biologist Dr. Chang proceeded on the most likely road. He “meddled” with Nature’s standard routine. Two prize animals were needed for conception, he reasoned—but why tie up the female for all the time needed to bring the offspring to the point of birth? Might it not be possible to take the prize female’s ovum soon after conception and transfer it for development to any ordinary female, valueless for breeding? The transplant would contain all the valuable gene combinations given it by its two prize parents; the second mother would merely supply blood for nourishment and a place to grow, without altering its heredity in any way. And the prize female would quickly be ready to start off another prize offspring in some other desired combination with a selected prize male.

All stock breeding experiments would be accelerated. Desirable strains would be produced much faster. And there would be much more prize stock around for both experiments and large-scale breeding.

No wonder the animal breeders hailed Dr. Chang’s “motherless” rabbits with enthusiasm.

And no wonder the geneticists were immediately interested too. Here was something new and practical—something which gave promise of adding a new chapter to human breeding.

It was because of their far shorter birth process and their small size and ease of handling that Dr. Chang chose to begin his experiments with rabbits.

He soon found that one of his big problems was that of keeping the fertilized eggs of the conceiving mother until they could be placed in the bearing mother. He worked at techniques. Now he can keep the fertilized eggs alive for as much as 144 hours before transplanting them to develop and be born.

He keeps them in a refrigerator!

Storage on ice—that is the thing that excites the animal breeders. Their artificial insemination technique is valuable, but it is restricted to the use of sperm cells. The sperm cells of prize cattle are used to fertilize prize females and thus produce more desirable stock; for example, it is common practice to preserve by refrigeration the sperm of famed Argentine bulls and fly it to various parts of this country. But because of the storability of transplants on ice, breeders now foresee the day when the prize cattle’s fertilized eggs themselves—not the sperm—can be preserved long enough for them to be flown wherever desired.

And then, arriving, they can be transplanted into mothers of ordinary breeding in the new country—as much as ten thousand miles away.

Dr. Chang found that transplanted fertilized eggs flourished. They grew just as big and healthy and the young finally were born just as normally as if it were their real mothers that were seeing them through their pre-natal life.

So—human mothers, in the days to come, need have no fear that fertilized ova transplanted to them will result in children that are not healthy and completely normal. Nor need unmarried women fear social ostracism by undertaking motherhood in this way. Of course the first cases may get publicity and cause comment; but it is difficult to see how anyone can criticize any woman who must remain unmarried, or who chooses to remain unmarried, and has a baby in this way. No breach of morality occurs.

Since it is normal for women to have children, and many women who can’t have them undergo psychological stresses, the transplant technique would fulfill them, and make them far more normal and valuable human beings. This is the case, too, with the many women who cannot or should not have children because of their own bad heredity, or that of their husband.

Toward all this, the first step, and probably the most important one, has already been made with Mrs. Rabbit. Here is what Dr. Chang did in his laboratory to arrive at his results: The eggs of super-ovulated rabbits (rabbits which can produce superior young) were stored in pure rabbit serum at low temperatures for varying lengths of time and then cultured at 37 degrees centigrade for 24 hours to determine whether they would grow normally. He was looking, at this stage, to see if normal cleavage, first step in development, would result.

He found that if he cooled the fertilized eggs rapidly from 25 to 0 degrees centigrade immediately after removing them from the mother rabbits, and then maintained them at the 37-degree temperature for a day, there would be no growth.

On the other hand, if he cooled the eggs slowly, from 25 to 0 in a five-hour period, he had happy results. This proved to him that the ova are subject to temperature shock upon rapid cooling but can be acclimatized to lower temperatures by gradual reduction.

Then Dr. Chang wanted to know—as did all animal breeders and geneticists along with him—just how long can these eggs be stored and still remain alive? He investigated, and found that at 10 degrees 53.8 per cent lived after 72 hours, and 23.6 after 144 hours.

Now Dr. Chang came to the vital question. Would these refrigerated babies-to-be develop into rabbits if he transplanted them into the bodies of female rabbits?

He injected the foster-mother rabbits with gonadtrophin to induce ovulation, rested them for 24 hours and then inserted the stored eggs into their Fallopian tubes. In each instance, from four to 15 eggs were transplanted into each rabbit.

It worked. Litter upon litter of fine, prize rabbits came from the foster-mothers. All the young were healthy, normal and genetically true to their real parents!

Telescoping Wings “Brake” Airplane

ONE of the most difficult problems of flying—that of reducing the speed of a high powered airplane to a minimum without slowing down the engine—has been solved to some extent by a Frenchman, M. Bille, who has invented an airplane in which
the wing surface can be mechanically increased, thus cutting down the speed of the machine.

Early inventions for varying the size of wings in flight lacked wing rigidity necessary to safe flying. Bille’s invention overcomes this handicap by means of two pairs of extension wings that telescope snugly into the main wings of the plane, so that they can be extended or taken in at will during flight.

At a recent demonstration of the plane Maneyrol, the French record making aviator, flew 100 miles an hour, then slowed down to 35 miles, and finally to 12 miles, simply by extending the wings. This was done in six seconds.