"Where is everyone?" Susan wondered as she crossed the deserted Crypto floor. Some emergency.

Although most NSA departments were fully staffed seven days a week, Crypto was generally quiet on Saturdays. Cryptographic mathematicians were by nature high-strung workaholics, and there existed an unwritten rule that they take Saturdays off except in emergencies. Code-breakers were too valuable a commodity at the NSA to risk losing them to burnout.

As Susan traversed the floor, TRANSLTR loomed to her right. The sound of the generators eight stories below sounded oddly ominous today. Susan never liked being in Crypto during off hours. It was like being trapped alone in a cage with some grand, futuristic beast. She quickly made her way toward the commander's office.

Strathmore's glass-walled workstation, nicknamed "the fishbowl" for its appearance when the drapes were open, stood high atop a set of catwalk stairs on the back wall of Crypto. As Susan climbed the grated steps, she gazed upward at Strathmore's thick, oak door. It bore the NSA seal-a bald eagle fiercely clutching an ancient skeleton key. Behind that door sat one of the greatest men she'd ever met.

Commander Strathmore, the fifty-six-year-old deputy director of operations, was like a father to Susan. He was the one who'd hired her, and he was the one who'd made the NSA her home. When Susan joined the NSA over a decade ago, Strathmore was heading the Crypto Development Division-a training ground for new cryptographers-new male cryptographers. Although Strathmore never tolerated the hazing of anyone, he was especially protective of his sole female staff member. When accused of favoritism, he simply replied with the truth: Susan Fletcher was one of the brightest young recruits he'd ever seen, and he had no intention of losing her to sexual harassment. One of the cryptographers foolishly decided to test Strathmore's resolve.

One morning during her first year, Susan dropped by the new cryptographers' lounge to get some paperwork. As she left, she noticed a picture of herself on the bulletin board. She almost fainted in embarrassment. There she was, reclining on a bed and wearing only panties.

As it turned out, one of the cryptographers had digitally scanned a photo from a pornographic magazine and edited Susan's head onto someone else's body. The effect had been quite convincing.

Unfortunately for the cryptographer responsible, Commander Strathmore did not find the stunt even remotely amusing. Two hours later, a landmark memo went out:

EMPLOYEE CARL AUSTIN TERMINATED FOR INAPPROPRIATE CONDUCT.

From that day on, nobody messed with her; Susan Fletcher was Commander Strathmore's golden girl.

But Strathmore's young cryptographers were not the only ones who learned to respect him; early in his career Strathmore made his presence known to his superiors by proposing a number of unorthodox and highly successful intelligence operations. As he moved up the ranks, Trevor Strathmore became known for his cogent, reductive analyses of highly complex situations. He seemed to have an uncanny ability to see past the moral perplexities surrounding the NSA's difficult decisions and to act without remorse in the interest of the common good.

There was no doubt in anyone's mind that Strathmore loved his country. He was known to his colleagues as a patriot and a visionary... a decent man in a world of lies.

In the years since Susan's arrival at the NSA, Strathmore had skyrocketed from head of Crypto Development to second-in-command of the entire NSA. Now only one man outranked Commander Strathmore there-Director Leland Fontaine, the mythical overlord of the Puzzle Palace-never seen, occasionally heard, and eternally feared. He and Strathmore seldom saw eye to eye, and when they met, it was like the clash of the titans. Fontaine was a giant among giants, but Strathmore didn't seem to care. He argued his ideas to the director with all the restraint of an impassioned boxer. Not even the President of the United States dared challenge Fontaine the way Strathmore did. One needed political immunity to do that-or, in Strathmore's case, political indifference.

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."