very day, millions of Americans tap into a sprawling global communications network, sending and receiving untold quantities of information through a largely insecure tapestry of copper wire and fiber-optic cable. As they transmit their orders and credit card numbers to online stores, dispatch confidential e-mail messages to friends or make long-distance calls with pre-paid calling cards, they leave footprints - traces of themselves and their private lives - behind on the digital landscape.

As you will see in our three "Secured" focus stories, the endless flow of information through the world's computer and telecommunications networks has become the subject of intense interest for researchers, businesses and entrepreneurs. Some of that interest revolves around the challenge of keeping track of those billions of bits and bytes. For Jay Gainsboro '75, that gargantuan task became the foundation of a successful business, one that catapulted him briefly into the national media spotlight.

Many others, including WPI professor Christof Paar and the alumni at GTE CyberTrust Solutions, are driven by a different challenge - finding ways to erase those virtual footprints, or at least hide them from information spies and thieves. The desire to keep information out of the hands of those who might illicitly profit from it has preoccupied governments, armies and businesses for centuries. In fact, historians of cryptography - the art and science of data scrambling - date the use of encryption back at least as far as 1900 BC.

With the rise of the Internet, the World Wide Web and the exploding domain of online commerce, the field of information security has taken on a new sense of urgency. The quest for newer, faster and more effective methods of encrypting information, and the equally compelling drive to break them, has become a high-stakes game of cat and mouse. It is a contest that marries the ancient mathematics of number theory with the latest high-tech tools of electrical and computer engineering.

While modern digital computers and global computer networks have opened up a new world of applications for cryptography, many of the challenges today's data scramblers face and many of the tools they use first made their appearance many years ago. In fact, the era of modern cryptography dawned 90 years ago with the brainstorm of Gilbert S. Vernam, a WPI graduate.

Vernam received his bachelor's degree in electrical engineering in 1914 and went to work for AT&T in New York. He joined a group of engineers who found themselves face to face with a conundrum that would sound quite familiar to cryptographers today: how to guarantee the security of private messages transmitted over a public communications network whose very design made it easy to intercept information. The network was not the Internet, of course, but the spider's web of telegraph wires that crisscrossed the nation.

The engineering group had been asked to study the security of the printing telegraph. They quickly discovered that even when multiple messages were speeding through a telegraph wire in both directions, a savvy hacker with an oscilloscope could monitor the frequency changes and transcribe the messages. After mulling the problem over, Vernam found an ingenious solution.

Printing telegraph machines typically used paper tapes for translating messages into electrical pulses and turning those pulses back into text. Vernam suggested using a second tape with a set of random pulses - a private key, in cryptographic terms - that would be added to the pulses of the text to create an encrypted message. An identical tape at the other end would enable the added pulses to be subtracted to reveal the message. Anyone intercepting the message would see only a meaningless jumble of pulses.

The idea of encrypting messages was nothing new. What Vernam accomplished was a method of coding and decoding messages automatically, in real time, which made cryptography, once a labor-intensive process that had to be done off-line, something that could be easily added to any communications system, from telephone calls, to radio transmissions, to e-mail messages flashed over the Internet.

Vernam's invention made him one of the "household names" of cryptography, and his accomplishments are included in many books on the field, including David Kahn's 1996 book The Codebreakers. Another seminal achievement in cryptography, the only unbreakable cryptosystem, called the one-time pad, is also often attributed to Vernam, because it arose from his invention of the encrypting telegraph machine.

Not long after he learned of Vernam's discovery, Major Joseph Mauborgne, head of the U.S. Army Signal Corps, discovered that if one employed a unique random key of the type developed by Vernam for each message and used each key only once, the result would be a system that even the most sophisticated code cracker could never break. Though impractical and rarely used (at least in commercial cryptography), such one-time systems are widely known in the field. (Interestingly, at press time, a firm known as Ultimate Privacy announced that it would market a cryptographic program for corporate networks that employs a one-time pad system.)

Vernam, who died in 1960, was president of the Wireless Association and a member of Tau Beta Pi, the engineering honor society, while at WPI. He spent 46 years in the communications field, earning 60 patents covering his work on cryptography, TWX systems, relay systems and switching centers. Nearly 40 years after his death, his work lives on in laboratories at WPI and around the world, where engineers, computer scientists and mathematicians continue the search for security that he began.