第 4 页

　* * *

　Susan arrived at the top of the stairs. Before she could knock, Strathmore's electronic door lock buzzed. The door swung open, and the commander waved her in.

　"Thanks for coming, Susan. I owe you one."

　"Not at all." She smiled as she sat opposite his desk.

　Strathmore was a rangy, thick-fleshed man whose muted features somehow disguised his hard-nosed efficiency and demand for perfection. His gray eyes usually suggested a confidence and discretion born from experience, but today they looked wild and unsettled.

　"You look beat," Susan said.

　"I've been better." Strathmore sighed.

　I'll say, she thought.

　Strathmore looked as bad as Susan had ever seen him. His thinning gray hair was disheveled, and even in the room's crisp air-conditioning, his forehead was beaded with sweat. He looked like he'd slept in his suit. He was sitting behind a modern desk with two recessed keypads and a computer monitor at one end. It was strewn with computer printouts and looked like some sort of alien cockpit propped there in the center of his curtained chamber.

　"Tough week?" she inquired.

　Strathmore shrugged. "The usual. The EFF's all over me about civilian privacy rights again."

　Susan chuckled. The EFF, or Electronics Frontier Foundation, was a worldwide coalition of computer users who had founded a powerful civil liberties coalition aimed at supporting free speech on-line and educating others to the realities and dangers of living in an electronic world. They were constantly lobbying against what they called "the Orwellian eavesdropping capabilities of government agencies"--particularly the NSA. The EFF was a perpetual thorn in Strathmore's side.

　"Sounds like business as usual," she said. "So what's this big emergency you got me out of the tub for?"

　Strathmore sat a moment, absently fingering the computer trackball embedded in his desktop. After a long silence, he caught Susan's gaze and held it. "What's the longest you've ever seen TRANSLTR take to break a code?"

　The question caught Susan entirely off guard. It seemed meaningless. This is what he called me in for?

　"Well..." She hesitated. "We hit a COMINT intercept a few months ago that took about an hour, but it had a ridiculously long key--ten thousand bits or something like that."

　Strathmore grunted. "An hour, huh? What about some of the boundary probes we've run?"

　Susan shrugged. "Well, if you include diagnostics, it's obviously longer."

　"How much longer?"

　Susan couldn't imagine what Strathmore was getting at. "Well, sir, I tried an algorithm last March with a segmented million-bit key. Illegal looping functions, cellular automata, the works. TRANSLTR still broke it."

　"How long?"

　"Three hours."

　Strathmore arched his eyebrows. "Three hours? That long?"

　Susan frowned, mildly offended. Her job for the last three years had been to fine-tune the most secret computer in the world; most of the programming that made TRANSLTR so fast was hers. A million-bit key was hardly a realistic scenario.

　"Okay," Strathmore said. "So even in extreme conditions, the longest a code has ever survived inside TRANSLTR is about three hours?"

　Susan nodded. "Yeah. More or less."

　Strathmore paused as if afraid to say something he might regret. Finally he looked up. "TRANSLTR's hit something..." He stopped.

　Susan waited. "More than three hours?"

　Strathmore nodded.

　She looked unconcerned. "A new diagnostic? Something from the Sys-Sec Department?"

　Strathmore shook his head. "It's an outside file."

　Susan waited for the punch line, but it never came. "An outside file? You're joking, right?"

　"I wish. I queued it last night around eleven thirty. It hasn't broken yet."

　Susan's jaw dropped. She looked at her watch and then back at Strathmore. "It's still going? Over fifteen hours?"

　Strathmore leaned forward and rotated his monitor toward Susan. The screen was black except for a small, yellow text box blinking in the middle.

　TIME ELAPSED: 15:09:33

　AWAITING KEY: ________

　Susan stared in amazement. It appeared TRANSLTR had been working on one code for over fifteen hours. She knew the computer's processors auditioned thirty million keys per second--one hundred billion per hour. If TRANSLTR was still counting, that meant the key had to be enormous--over ten billion digits long. It was absolute insanity.

　"It's impossible!" she declared. "Have you checked for error flags? Maybe TRANSLTR hit a glitch and--"

　"The run's clean."

　"But the pass-key must be huge!"

　Strathmore shook his head. "Standard commercial algorithm. I'm guessing a sixty-four-bit key."

　Mystified, Susan looked out the window at TRANSLTR below. She knew from experience that it could locate a sixty-four-bit key in under ten minutes. "There's got to be some explanation."

　Strathmore nodded. "There is. You're not going to like it."

　Susan looked uneasy. "Is TRANSLTR malfunctioning?"

　"TRANSLTR's fine."

　"Have we got a virus?"

　Strathmore shook his head. "No virus. Just hear me out."

　Susan was flabbergasted. TRANSLTR had never hit a code it couldn't break in under an hour. Usually the cleartext was delivered to Strathmore's printout module within minutes. She glanced at the high-speed printer behind his desk. It was empty.

　"Susan," Strathmore said quietly. "This is going to be hard to accept at first, but just listen a minute." He chewed his lip. "This code that TRANSLTR's working on--it's unique. It's like nothing we've ever seen before." Strathmore paused, as if the words were hard for him to say. "This code is unbreakable."

　Susan stared at him and almost laughed. Unbreakable? What was THAT supposed to mean? There was no such thing as an unbreakable code--some took longer than others, but every code was breakable. It was mathematically guaranteed that sooner or later TRANSLTR would guess the right key. "I beg your pardon?"

　"The code's unbreakable," he repeated flatly.

　Unbreakable? Susan couldn't believe the word had been uttered by a man with twenty-seven years of code analysis experience.

　"Unbreakable, sir?" she said uneasily. "What about the Bergofsky Principle?"

　Susan had learned about the Bergofsky Principle early in her career. It was a cornerstone of brute-force technology. It was also Strathmore's inspiration for building TRANSLTR. The principle clearly stated that if a computer tried enough keys, it was mathematically guaranteed to find the right one. A code's security was not that its pass-key was unfindable but rather that most people didn't have the time or equipment to try.

　Strathmore shook his head. "This code's different."

　"Different?" Susan eyed him askance. An unbreakable code is a mathematical impossibility! He knows that!

　Strathmore ran a hand across his sweaty scalp. "This code is the product of a brand-new encryption algorithm--one we've never seen before."

　Now Susan was even more doubtful. Encryption algorithms were just mathematical formulas, recipes for scrambling text into code. Mathematicians and programmers created new algorithms every day. There were hundreds of them on the market--PGP, Diffie-Hellman, ZIP, IDEA, El Gamal. TRANSLTR broke all of their codes every day, no problem. To TRANSLTR all codes looked identical, regardless of which algorithm wrote them.

　"I don't understand," she argued. "We're not talking about reverse-engineering some complex function, we're talking brute force. PGP, Lucifer, DSA--it doesn't matter. The algorithm generates a key it thinks is secure, and TRANSLTR keeps guessing until it finds it."

　Strathmore's reply had the controlled patience of a good teacher. "Yes, Susan, TRANSLTR will always find the key--even if it's huge." He paused a long moment. "Unless..."

　Susan wanted to speak, but it was clear Strathmore was about to drop his bomb. Unless what?

　"Unless the computer doesn't know when it's broken the code."

　Susan almost fell out of her chair. "What!"

　"Unless the computer guesses the correct key but just keeps guessing because it doesn't realize it found the right key." Strathmore looked bleak. "I think this algorithm has got a rotating cleartext."

　Susan gaped.

　The notion of a rotating cleartext function was first put forth in an obscure, 1987 paper by a Hungarian mathematician, Josef Harne. Because brute-force computers broke codes by examining cleartext for identifiable word patterns, Harne proposed an encryption algorithm that, in addition to encrypting, shifted decrypted cleartext over a time variant. In theory, the perpetual mutation would ensure that the attacking computer would never locate recognizable word patterns and thus never know when it had found the proper key. The concept was somewhat like the idea of colonizing Mars--fathomable on an intellectual level, but, at present, well beyond human ability.

　"Where did you get this thing?" she demanded.

　The commander's response was slow. "A public sector programmer wrote it."

　"What?" Susan collapsed back in her chair. "We've got the best programmers in the world downstairs! All of us working together have never even come close to writing a rotating cleartext function. Are you trying to tell me some punk with a PC figured out how to do it?"

　Strathmore lowered his voice in an apparent effort to calm her. "I wouldn't call this guy a punk."

　Susan wasn't listening. She was convinced there had to be some other explanation: A glitch. A virus. Anything was more likely than an unbreakable code.

　Strathmore eyed her sternly. "One of the most brilliant cryptographic minds of all time wrote this algorithm."

　Susan was more doubtful than ever; the most brilliant cryptographic minds of all time were in her department, and she certainly would have heard about an algorithm like this.

　"Who?" she demanded.

　"I'm sure you can guess." Strathmore said. "He's not too fond of the NSA."

　"Well, that narrows it down!" she snapped sarcastically.

　"He worked on the TRANSLTR project. He broke the rules. Almost caused an intelligence nightmare. I deported him."

　Susan's face was blank only an instant before going white. "Oh my God..."

　Strathmore nodded. "He's been bragging all year about his work on a brute-force–resistant algorithm."

　"B-but..." Susan stammered. "I thought he was bluffing. He actually did it?"

　"He did. The ultimate unbreakable code-writer."

　Susan was silent a long moment. "But... that means..."

　Strathmore looked her dead in the eye. "Yes. Ensei Tankado just made TRANSLTR obsolete."

　CHAPTER?6

　Although Ensei Tankado was not alive during the Second World War, he carefully studied everything about it--particularly about its culminating event, the blast in which 100,000 of his countrymen where incinerated by an atomic bomb.

　Hiroshima, 8:15 a.m. August 6, 1945--a vile act of destruction. A senseless display of power by a country that had already won the war. Tankado had accepted all that. But what he could never accept was that the bomb had robbed him of ever knowing his mother. She had died giving birth to him--complications brought on by the radiation poisoning she'd suffered so many years earlier.

　In 1945, before Ensei was born, his mother, like many of her friends, traveled to Hiroshima to volunteer in the burn centers. It was there that she became one of the hibakusha--the radiated people. Nineteen years later, at the age of thirty-six, as she lay in the delivery room bleeding internally, she knew she was finally going to die. What she did not know was that death would spare her the final horror--her only child was to be born deformed.

　Ensei's father never even saw his son. Bewildered by the loss of his wife and shamed by the arrival of what the nurses told him was an imperfect child who probably would not survive the night, he disappeared from the hospital and never came back. Ensei Tankado was placed in a foster home.

　Every night the young Tankado stared down at the twisted fingers holding his daruma wish-doll and swore he'd have revenge--revenge against the country that had stolen his mother and shamed his father into abandoning him. What he didn't know was that destiny was about to intervene.

　In February of Ensei's twelfth year, a computer manufacturer in Tokyo called his foster family and asked if their crippled child might take part in a test group for a new keyboard they'd developed for handicapped children. His family agreed.

　Although Ensei Tankado had never seen a computer, it seemed he instinctively knew how to use it. The computer opened worlds he had never imagined possible. Before long it became his entire life. As he got older, he gave classes, earned money, and eventually earned a scholarship to Doshisha University. Soon Ensei Tankado was known across Tokyo as fugusha kisai--the crippled genius.

　Tankado eventually read about Pearl Harbor and Japanese war crimes. His hatred of America slowly faded. He became a devout Buddhist. He forgot his childhood vow of revenge; forgiveness was the only path to enlightenment.

　By the time he was twenty, Ensei Tankado was somewhat of an underground cult figure among programmers. IBM offered him a work visa and a post in Texas. Tankado jumped at the chance. Three years later he had left IBM, was living in New York, and was writing software on his own. He rode the new wave of public-key encryption. He wrote algorithms and made a fortune.

　Like many of the top authors of encryption algorithms, Tankado was courted by the NSA. The irony was not lost on him--the opportunity to work in the heart of the government in a country he had once vowed to hate. He decided to go on the interview. Whatever doubts he had disappeared when he met Commander Strathmore. They talked frankly about Tankado's background, the potential hostility he might feel toward the U.S., his plans for the future. Tankado took a polygraph test and underwent five weeks of rigorous psychological profiles. He passed them all. His hatred had been replaced by his devotion to Buddha. Four months later Ensei Tankado went to work in the Cryptography Department of the National Security Agency.