Susan was amazed. The formula for Digital Fortress had beenencrypted using Digital Fortress. Tankado had posted a pricelessmathematical recipe, but the text of the recipe had been scrambled.And it had used itself to do the scrambling.

"It's Biggleman's Safe," Susan stammered inawe. Strathmore nodded. Biggleman's Safe was a hypotheticalcryptography scenario in which a safe builder wrote blueprints foran unbreakable safe. He wanted to keep the blueprints a secret, sohe built the safe and locked the blueprints inside. Tankado haddone the same thing with Digital Fortress. He'd protected hisblueprints by encrypting them with the formula outlined in hisblueprints.

"And the file in TRANSLTR?" Susan asked.

"I downloaded it from Tankado's Internet site likeeveryone else. The NSA is now the proud owner of the DigitalFortress algorithm; we just can't open it."

Susan marveled at Ensei Tankado's ingenuity. Withoutrevealing his algorithm, he had proven to the NSA that it wasunbreakable.

Strathmore handed her a newspaper clipping. It was a translatedblurb from the Nikkei Shimbun, the j.a.panese equivalent of the WallStreet Journal, stating that the j.a.panese programmer Ensei Tankadohad completed a mathematical formula he claimed could writeunbreakable codes. The formula was called Digital Fortress and wasavailable for review on the Internet. The programmer would beauctioning it off to the highest bidder. The column went on to saythat although there was enormous interest in j.a.pan, the few U.S.software companies who had heard about Digital Fortress deemed theclaim preposterous, akin to turning lead to gold. The formula, theysaid, was a hoax and not to be taken seriously.

Susan looked up. "An auction?"

Strathmore nodded. "Right now every software company inj.a.pan has downloaded an encrypted copy of Digital Fortress and istrying to crack it open. Every second they can't, the biddingprice climbs."

"That's absurd," Susan shot back. "All thenew encrypted files are uncrackable unless you have TRANSLTR.Digital Fortress could be nothing more than a generic,public- domain algorithm, and none of these companies could breakit."

"But it's a brilliant marketing ploy," Strathmoresaid. "Think about it-all brands of bulletproof gla.s.sstop bullets, but if a company dares you to put a bullet throughtheirs, suddenly everybody's trying."

"And the j.a.panese actually believe Digital Fortressis different? Better than everything else on the market?"

"Tankado may have been shunned, but everybody knowshe's a genius. He's practically a cult icon amonghackers. If Tankado says the algorithm's unbreakable,it's unbreakable."

But they're all unbreakable as far as the publicknows!"

"Yes ..." Strathmore mused. "For themoment."

"What's that supposed to mean?" Strathmore sighed. "Twenty years ago no one imaginedwe'd be breaking twelve-bit stream ciphers. But technologyprogressed. It always does. Software manufacturers a.s.sume at somepoint computers like TRANSLTR will exist. Technology is progressingexponentially, and eventually current public-key algorithms willlose their security. Better algorithms will be needed to stay aheadof tomorrow's computers."

"And Digital Fortress is it?"

"Exactly. An algorithm that resists brute force will neverbecome obsolete, no matter how powerful code-breaking computersget. It could become a world standard overnight."

Susan pulled in a long breath. "G.o.d help us," shewhispered. "Can we make a bid?"

Strathmore shook his head. "Tankado gave us our chance. Hemade that clear. It's too risky anyway; if we get caught,we're basically admitting that we're afraid of hisalgorithm. We'd be making a public confession not only that wehave TRANSLTR but that Digital Fortress is immune."

"What's the time frame?"

Strathmore frowned. "Tankado planned to announce thehighest bidder tomorrow at noon."

Susan felt her stomach tighten. "Then what?"

"The arrangement was that he would give the winner thepa.s.s-key."

"The pa.s.s-key?"

"Part of the ploy. Everybody's already got thealgorithm, so Tankado's auctioning off the pa.s.s-key thatunlocks it."

Susan groaned. "Of course." It was perfect. Clean andsimple. Tankado had encrypted Digital Fortress, and he alone heldthe pa.s.s-key that unlocked it. She found it hard to fathom thatsomewhere out there-probably scrawled on a piece of paper inTankado's pocket-there was a sixty-four-characterpa.s.s-key that could end U.S. intelligence gathering forever.

Susan suddenly felt ill as she imagined the scenario. Tankadowould give his pa.s.s-key to the highest bidder, and that companywould unlock the Digital Fortress file. Then it probably wouldembed the algorithm in a tamper-proof chip, and within five yea.r.s.every computer would come preloaded with a Digital Fortress chip.No commercial manufacturer had ever dreamed of creating anencryption chip because normal encryption algorithms eventuallybecome obsolete. But Digital Fortress would never become obsolete;with a rotating cleartext function, no brute-force attack wouldever find the right key. A new digital encryption standard. Fromnow until forever. Every code unbreakable. Bankers, brokers,terrorists, spies. One world-one algorithm. Anarchy.

"What are the options?" Susan probed. She was wellaware that desperate times called for desperate measures, even atthe NSA.

"We can't remove him, if that's what you'reasking."

It was exactly what Susan was asking. In her years with the NSA,Susan had heard rumors of its loose affiliations with the mostskilled a.s.sa.s.sins in the world-hired hands brought in to dothe intelligence community's dirty work.

Strathmore shook his head. "Tankado's too smart toleave us an option like that."

Susan felt oddly relieved. "He's protected?"

"Not exactly."

"In hiding?"

Strathmore shrugged. "Tankado left j.a.pan. He planned tocheck his bids by phone. But we know where he is."

"And you don't plan to make a move?"

"No. He's got insurance. Tankado gave a copy of hispa.s.s-key to an anonymous third party ... in case anythinghappened."

Of course, Susan marveled. A guardian angel."And I suppose if anything happens to Tankado, the mystery mansells the key?"

"Worse. Anyone hits Tankado, and his partnerpublishes."

Susan looked confused. "His partner publishes thekey?"

Strathmore nodded. "Posts it on the Internet, puts it innewspapers, on billboards. In effect, he gives itaway."

Susan's eyes widened. "Free downloads?"

"Exactly. Tankado figured if he was dead, he wouldn'tneed the money-why not give the world a little farewellgift?"

There was a long silence. Susan breathed deeply as if to absorbthe terrifying truth.

Ensei Tankado has created an unbreakablealgorithm. He's holding us hostage.

She suddenly stood. Her voice was determined. "We mustcontact Tankado! There must be a way to convince him not torelease! We can offer him triple the highest bid!

We can clear hisname! Anything!" "Too late," Strathmore said. He took a deep breath."Ensei Tankado was found dead this morning in Seville,Spain."

CHAPTER 8

The twin-engine Learjet 60 touched down on the scorching runway.Outside the window, the barren landscape of Spain's lowerextremadura blurred and then slowed to a crawl.

"Mr. Becker?" a voice crackled. "We'rehere."

Becker stood and stretched. After unlatching the overheadcompartment, he remembered he had no luggage. There had been notime to pack. It didn't matter- he'd been promisedthe trip would be brief, in and out.

As the engines wound down, the plane eased out of the sun andinto a deserted hangar opposite the main terminal. A moment laterthe pilot appeared and popped the hatch.

Becker tossed back thelast of his cranberry juice, put the gla.s.s on the wet bar, andscooped up his suit coat.

The pilot pulled a thick manila envelope from his flight suit."I was instructed to give you this." He handed it toBecker. On the front, scrawled in blue pen, were the words: KEEP THE CHANGE.

Becker thumbed through the thick stack of reddish bills."What the ... ?"

"Local currency," the pilot offered flatly.

"I know what it is," Becker stammered. "But.i.t's ... it's too much. All I need is taxi fare."Becker did the conversion in his head. "What's in here isworth thousands of dollars!"

"I have my orders, sir." The pilot turned and hoistedhimself back into the cabin. The door slid shut behind him.

Becker stared up at the plane and then down at the money in hishand. After standing a moment in the empty hangar, he put theenvelope in his breast pocket, shouldered his suit coat, and headedout across the runway. It was a strange beginning. Becker pushed itfrom his mind. With a little luck he'd be back in time tosalvage some of his Stone Manor trip with Susan. In and out, he told himself. In and out.

There was no way he could have known.

CHAPTER 9

Systems security technician Phil Chartrukian had only intendedto be inside Crypto a minute-just long enough to grab somepaperwork he'd forgotten the day before. But it was not tobe.

After making his way across the Crypto floor and stepping intothe Sys-Sec lab, he immediately knew something was not right. Thecomputer terminal that perpetually monitored TRANSLTR'sinternal workings was unmanned and the monitor was switchedoff.

Chartrukian called out, "h.e.l.lo?"

There was no reply. The lab was spotless-as if no one hadbeen there for hours.

Although Chartrukian was only twenty-three and relatively new tothe Sys-Sec squad, he'd been trained well, and he knew thedrill: There was always a Sys-Sec on duty in Crypto ...especially on Sat.u.r.days when no cryptographers were around.

He immediately powered up the monitor and turned to the dutyboard on the wall.

"Who's on watch?" he demandedaloud, scanning the list of names. According to the schedule, ayoung rookie named Seidenberg was supposed to have started a doubleshift at midnight the night before. Chartrukian glanced around theempty lab and frowned. "So where the h.e.l.l is he?"

As he watched the monitor power up, Chartrukian wondered ifStrathmore knew the Sys-Sec lab was unmanned. He had noticed on hisway in that the curtains of Strathmore's workstation wereclosed, which meant the boss was in-not at all uncommon for aSat.u.r.day; Strathmore, despite requesting his cryptographers takeSat.u.r.days off, seemed to work 365 days a year.

There was one thing Chartrukian knew for certain-ifStrathmore found out the Sys- Sec lab was unmanned, it would costthe absent rookie his job. Chartrukian eyed the phone, wondering ifhe should call the young techie and bail him out; there was anunspoken rule among Sys-Sec that they would watch each other'sbacks. In Crypto, Sys-Secs were second-cla.s.s citizens, constantlyat odds with the lords of the manor. It was no secret that thecryptographers ruled this multibillion-dollar roost; Sys-Secs weretolerated only because they kept the toys running smoothly.

Chartrukian made his decision. He grabbed the phone. But thereceiver never reached his ear. He stopped short, his eyestransfixed on the monitor now coming into focus before him. As ifin slow motion, he set down the phone and stared in open- mouthedwonder.

In eight months as a Sys-Sec, Phil Chartrukian had never seenTRANSLTR's Run- Monitor post anything other than a double zeroin the hours field. Today was a first.

TIME ELAPSED: 15:17:21 "Fifteen hours and seventeen minutes?" he choked."Impossible!"

He rebooted the screen, praying it hadn't refreshedproperly. But when the monitor came back to life, it looked thesame.

Chartrukian felt a chill. Crypto's Sys-Secs had only oneresponsibility: Keep TRANSLTR "clean"-virusfree.

Chartrukian knew that a fifteen-hour run could only mean onething-infection. An impure file had gotten inside TRANSLTR andwas corrupting the programming.

Instantly his training kicked in;it no longer mattered that the Sys-Sec lab had been unmanned or themonitors switched off. He focused on the matter athand- TRANSLTR. He immediately called up a log of all the filesthat had entered TRANSLTR in the last forty-eight hours. He beganscanning the list.

Did an infected file get through? he wondered. Couldthe security filters have missed something?

As a precaution, every file entering TRANSLTR had to pa.s.sthrough what was known as Gauntlet-a series of powerfulcircuit-level gateways, packet filters, and disinfectant programsthat scanned inbound files for computer viruses and potentiallydangerous subroutines. Files containing programming"unknown" to Gauntlet were immediately rejected. They hadto be checked by hand. Occasionally Gauntlet rejected entirelyharmless files on the basis that they contained programming thefilters had never seen before. In that case, the Sys-Secs did ascrupulous manual inspection, and only then, on confirmation thatthe file was clean, did they bypa.s.s Gauntlet's filters andsend the file into TRANSLTR.

Computer viruses were as varied as bacterial viruses. Like theirphysiological counterparts, computer viruses had one goal-toattach themselves to a host system and replicate. In this case, thehost was TRANSLTR.

Chartrukian was amazed the NSA hadn't had problems withviruses before. Gauntlet was a potent sentry, but still, the NSAwas a bottom feeder, sucking in ma.s.sive amounts of digitalinformation from systems all over the world. Snooping data was alot like having indiscriminate s.e.x-protection or noprotection, sooner or later you caught something. Chartrukian finished examining the file list before him. He wasnow more puzzled than before. Every file checked out. Gauntlet hadseen nothing out of the ordinary, which meant the file in TRANSLTRwas totally clean.

"So what the h.e.l.l's taking so long?" he demandedof the empty room. Chartrukian felt himself break a sweat. Hewondered if he should go disturb Strathmore with the news.

"A virus probe," Chartrukian said firmly, trying tocalm himself down. "I should run a virus probe."

Chartrukian knew that a virus probe would be the first thingStrathmore would request anyway. Glancing out at the desertedCrypto floor, Chartrukian made his decision. He loaded the viralprobe software and launched it. The run would take about fifteenminutes.

"Come back clean," he whispered. "Squeaky clean.Tell Daddy it's nothing."

But Chartrukian sensed it was not "nothing."Instinct told him something very unusual was going on inside thegreat decoding beast.

CHAPTER 10

"Ensei Tankado is dead?" Susan felt a wave of nausea."You killed him? I thought you said-"