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

Susan had learned about the Bergofsky Principle early in hercareer. It was a cornerstone of brute-force technology. It was alsoStrathmore's inspiration for building TRANSLTR. The principleclearly stated that if a computer tried enough keys, it wasmathematically guaranteed to find the right one. A code'ssecurity was not that its pa.s.s-key was unfindable but rather thatmost people didn't have the time or equipment to try.

Strathmore shook his head. "This code'sdifferent."

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

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

Now Susan was even more doubtful. Encryption algorithms werejust 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-h.e.l.lman,ZIP, IDEA, El Gamal. TRANSLTR broke all of their codes every day,no problem. To TRANSLTR all codes looked identical, regardless ofwhich algorithm wrote them.

"I don't understand," she argued."We're not talking about reverse-engineering some complexfunction, we're talking brute force. PGP, Lucifer, DSA-itdoesn't matter.

The algorithm generates a key it thinks issecure, and TRANSLTR keeps guessing until it finds it."

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

Susan wanted to speak, but it was clear Strathmore was about todrop his bomb.

Unless what?

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

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

"Unless the computer guesses the correct key but just keepsguessing because it doesn't realize it found the rightkey." Strathmore looked bleak. "I think this algorithmhas got a rotating cleartext."

Susan gaped.

The notion of a rotating cleartext function was first put forthin an obscure, 1987 paper by a Hungarian mathematician, JosefHarne. Because brute-force computers broke codes by examiningcleartext for identifiable word patterns, Harne proposed anencryption algorithm that, in addition to encrypting, shifteddecrypted cleartext over a time variant. In theory, the perpetualmutation would ensure that the attacking computer would neverlocate recognizable word patterns and thus never know when it hadfound the proper key. The concept was somewhat like the idea ofcolonizing Mars-fathomable on an intellectual level, but, atpresent, well beyond human ability. "Where did you get this thing?" she demanded.

The commander's response was slow. "A public sectorprogrammer 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 towriting a rotating cleartext function. Are you trying to tell mesome 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 besome other explanation: A glitch. A virus. Anything was more likelythan an unbreakable code.

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

Susan was more doubtful than ever; the most brilliantcryptographic minds of all time were in her department, and shecertainly 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 snappedsarcastically.

"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 G.o.d ..."

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

"B-but ..." Susan stammered. "I thought he wasbluffing. 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 Tankadojust made TRANSLTR obsolete."

CHAPTER 6

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

Hiroshima, 8:15 a.m. August 6, 1945-a vile act ofdestruction. A senseless display of power by a country that hadalready won the war. Tankado had accepted all that. But what hecould never accept was that the bomb had robbed him of ever knowinghis mother. She had died giving birth to him-complicationsbrought on by the radiation poisoning she'd suffered so manyyears earlier.

In 1945, before Ensei was born, his mother, like many of herfriends, traveled to Hiroshima to volunteer in the burn centers. Itwas there that she became one of the hibakusha-the radiatedpeople. Nineteen years later, at the age of thirty-six, as she layin the delivery room bleeding internally, she knew she was finallygoing to die.

What she did not know was that death would spare herthe final horror-her only child was to be born deformed.

Ensei's father never even saw his son. Bewildered by theloss of his wife and shamed by the arrival of what the nurses toldhim was an imperfect child who probably would not survive thenight, he disappeared from the hospital and never came back.

EnseiTankado was placed in a foster home.

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

In February of Ensei's twelfth year, a computermanufacturer in Tokyo called his foster family and asked if theircrippled child might take part in a test group for a new keyboardthey'd developed for handicapped children. His familyagreed.

Although Ensei Tankado had never seen a computer, it seemed heinstinctively knew how to use it. The computer opened worlds he hadnever imagined possible. Before long it became his entire life. Ashe got older, he gave cla.s.ses, earned money, and eventually earneda scholarship to Doshisha University. Soon Ensei Tankado was knownacross Tokyo as fugusha kisai-the crippled genius.

Tankado eventually read about Pearl Harbor and j.a.panese warcrimes. His hatred of America slowly faded. He became a devoutBuddhist. He forgot his childhood vow of revenge; forgiveness wasthe only path to enlightenment.

By the time he was twenty, Ensei Tankado was somewhat of anunderground cult figure among programmers. IBM offered him a workvisa and a post in Texas.

Tankado jumped at the chance. Three yearslater he had left IBM, was living in New York, and was writingsoftware 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, Tankadowas courted by the NSA. The irony was not lost on him-theopportunity to work in the heart of the government in a country hehad once vowed to hate. He decided to go on the interview. Whateverdoubts he had disappeared when he met Commander Strathmore.

Theytalked frankly about Tankado's background, the potentialhostility he might feel toward the U.S., his plans for the future.Tankado took a polygraph test and underwent five weeks of rigorouspsychological profiles. He pa.s.sed them all. His hatred had beenreplaced by his devotion to Buddha. Four months later Ensei Tankadowent to work in the Cryptography Department of the NationalSecurity Agency.

Despite his large salary, Tankado went to work on an old Mopedand ate a bag lunch alone at his desk instead of joining the restof the department for prime rib and vichyssoise in the commissary.The other cryptographers revered him. He was brilliant-ascreative a programmer as any of them had ever seen. He was kind andhonest, quiet, and of impeccable ethics. Moral integrity was ofparamount importance to him. It was for this reason that hisdismissal from the NSA and subsequent deportation had been such ashock.

Tankado, like the rest of the Crypto staff, had been working onthe TRANSLTR project with the understanding that if successful, itwould be used to decipher E-mail only in cases preapproved by theJustice Department. The NSA's use of TRANSLTR was to beregulated in much the same way the FBI needed a federal court orderto install a wiretap. TRANSLTR was to include programming thatcalled for pa.s.swords held in escrow by the Federal Reserve and theJustice Department in order to decipher a file. This would preventthe NSA from listening indiscriminately to the personalcommunications of law-abiding citizens around the globe.

However, when the time came to enter that programming, theTRANSLTR staff was told there had been a change of plans. Becauseof the time pressures often a.s.sociated with the NSA'sant.i.terrorist work, TRANSLTR was to be a free-standing decryptiondevice whose day-to-day operation would be regulated solely by theNSA.

Ensei Tankado was outraged. This meant the NSA would, in effect,be able to open everyone's mail and reseal it without theirknowing. It was like having a bug in every phone in the world.Strathmore attempted to make Tankado see TRANSLTR as alaw- enforcement device, but it was no use; Tankado was adamant that.i.t const.i.tuted a gross violation of human rights. He quit on thespot and within hours violated the NSA's code of secrecy bytrying to contact the Electronic Frontier Foundation. Tankado stoodpoised to shock the world with his story of a secret machinecapable of exposing computer users around the world to unthinkablegovernment treachery. The NSA had had no choice but to stophim.

Tankado's capture and deportation, widely publicized amongon-line newsgroups, had been an unfortunate public shaming. AgainstStrathmore's wishes, the NSA damage- controlspecialists-nervous that Tankado would try to convince peopleof TRANSLTR's existence-generated rumors that destroyedhis credibility. Ensei Tankado was shunned by the global computercommunity-n.o.body trusted a cripple accused of spying,particularly when he was trying to buy his freedom with absurdallegations about a U.S. code-breaking machine.

The oddest thing of all was that Tankado seemed to understand;it was all part of the intelligence game. He appeared to harbor noanger, only resolve. As security escorted him away, Tankado spokehis final words to Strathmore with a chilling calm.

"We all have a right to keep secrets," he'd said."Someday I'll see to it we can."

CHAPTER 7

Susan's mind was racing-Ensei Tankado wrote aprogram that creates unbreakable codes! She could barely graspthe thought.

"Digital Fortress," Strathmore said. "That'swhat he's calling it. It's the ultimatecounterintelligence weapon. If this program hits the market, everythird grader with a modem will be able to send codes the NSAcan't break. Our intelligence will be shot."

But Susan's thoughts were far removed from the politicalimplications of Digital Fortress. She was still struggling tocomprehend its existence. She'd spent her life breaking codes,firmly denying the existence of the ultimate code. Every code isbreakable-the Bergofsky Principle! She felt like anatheist coming face to face with G.o.d.

"If this code gets out," she whispered,"cryptography will become a dead science."

Strathmore nodded. "That's the least of ourproblems."

"Can we pay Tankado off? I know he hates us, but can'twe offer him a few million dollars? Convince him not todistribute?"

Strathmore laughed. "A few million? Do you know what thisthing is worth? Every government in the world will bid top dollar.Can you imagine telling the President that we're stillcable-snooping the Iraqis but we can't read the interceptsanymore? This isn't just about the NSA, it's about theentire intelligence community. This facility provides support foreveryone-the FBI, CIA, DEA; they'd all be flying blind.The drug cartels' shipments would become untraceable, majorcorporations could transfer money with no paper trail and leave theIRS out in the cold, terrorists could chat in total secrecy-itwould be chaos."

"The EFF will have field day," Susan said, pale.

"The EFF doesn't have the first clue about what we dohere," Strathmore railed in disgust. "If they knew howmany terrorist attacks we've stopped because we can decryptcodes, they'd change their tune."

Susan agreed, but she also knew the realities; the EFF wouldnever know how important TRANSLTR was. TRANSLTR had helped foildozens of attacks, but the information was highly cla.s.sified andwould never be released. The rationale behind the secrecy wa.s.simple: The government could not afford the ma.s.s hysteria caused byrevealing the truth; no one knew how the public would react to thenews that there had been two nuclear close calls by fundamentalistgroups on U.S. soil in the last year.

Nuclear attack, however, was not the only threat. Only lastmonth TRANSLTR had thwarted one of the most ingeniously conceivedterrorist attacks the NSA had ever witnessed. An antigovernmentorganization had devised a plan, code-named Sherwood Forest. Ittargeted the New York Stock Exchange with the intention of"redistributing the wealth." Over the course of six days,members of the group placed twenty-seven nonexplosive flux pods inthe buildings surrounding the Exchange. These devices, whendetonated, create a powerful blast of magnetism. The simultaneousdischarge of these carefully placed pods would create a magneticfield so powerful that all magnetic media in the Stock Exchangewould be erased-computer hard drives, ma.s.sive ROM storagebanks, tape backups, and even floppy disks. All records of whoowned what would disintegrate permanently.

Because pinpoint timing was necessary for simultaneousdetonation of the devices, the flux pods were interconnected overInternet telephone lines. During the two-day countdown, thepods' internal clocks exchanged endless streams of encryptedsynchronization data. The NSA intercepted the data-pulses as anetwork anomaly but ignored them as a seemingly harmless exchangeof gibberish. But after TRANSLTR decrypted the data streams,a.n.a.lysts immediately recognized the sequence as anetwork-synchronized countdown. The pods were located and removed afull three hours before they were scheduled to go off.

Susan knew that without TRANSLTR the NSA was helpless againstadvanced electronic terrorism. She eyed the Run-Monitor. It stillread over fifteen hours. Even if Tankado's file broke rightnow, the NSA was sunk. Crypto would be relegated to breaking lessthan two codes a day. Even at the present rate of 150 a day, therewas still a backlog of files awaiting decryption.

"Tankado called me last month," Strathmore said,interrupting Susan's thoughts.

Susan looked up. "Tankado called you?"

He nodded. "To warn me." "Warn you? He hates you."

"He called to tell me he was perfecting an algorithm thatwrote unbreakable codes. I didn't believe him."

"But why would he tell you about it?" Susan demanded."Did he want you to buy it?"

"No. It was blackmail."

Things suddenly began falling into place for Susan. "Ofcourse," she said, amazed.

"He wanted you to clear hisname."

"No," Strathmore frowned. "Tankado wantedTRANSLTR."

"TRANSLTR?"

"Yes. He ordered me to go public and tell the world we haveTRANSLTR. He said if we admitted we can read public E-mail, hewould destroy Digital Fortress."

Susan looked doubtful.

Strathmore shrugged. "Either way, it's too late now.He's posted a complimentary copy of Digital Fortress at hisInternet site. Everyone in the world can download it."

Susan went white. "He what!"

"It's a publicity stunt. Nothing to worry about. Thecopy he posted is encrypted.

People can download it, but n.o.body canopen it. It's ingenious, really. The source code for DigitalFortress has been encrypted, locked shut."

Susan looked amazed. "Of course! So everybody can have a copy, but n.o.body can open it."

"Exactly. Tankado's dangling a carrot."

"Have you seen the algorithm?"

The commander looked puzzled. "No, I told you it'sencrypted."

Susan looked equally puzzled. "But we've got TRANSLTR;why not just decrypt it?"

But when Susan saw Strathmore'sface, she realized the rules had changed. "Oh my G.o.d."She gasped, suddenly understanding. "Digital Fortress isencrypted with itself?"

Strathmore nodded. "Bingo."