Digital Fortress

Prowling hackers were now appearing from all over the world. The number was doubling almost every minute. Before long, anyone with a computer-foreign spies, radicals, terrorists-would have access to all of the U.S. government’s classified information.

As technicians tried vainly to sever power, the assembly on the podium studied the message. Even David and the two NSA agents were trying to crack the code from their van in Spain.

PRIME DIFFERENCE BETWEEN ELEMENTS RESPONSIBLE FORHIROSHIMA AND NAGASAKI

Soshi thought aloud. "The elements responsible for Hiroshima and Nagasaki… Pearl Harbor? Hirohito’s refusal to…"

"We need a number," Jabba repeated, "not political theories. We’re talking mathematics-not history!"

Soshi fell silent.

"How about payloads?" Brinkerhoff offered. "Casualties? Dollars damage?"

"We’re looking for an exact figure," Susan reminded. "Damage estimates vary." She stared up at the message. "The elements responsible…"

Three thousand miles away, David Becker’s eyes flew open. "Elements!" he declared. "We’re talking math, not history!"

All heads turned toward the satellite screen.

"Tankado’s playing word games!" Becker spouted. "The word ‘elements’ has multiple meanings!"

"Spit it out, Mr. Becker," Fontaine snapped.

"He’s talking about chemical elements-not sociopolitical ones!"

Becker’s announcement met blank looks.

"Elements!" he prompted. "The periodic table! Chemical elements! Didn’t any of you see the movie Fat Man and Little Boy-about the Manhattan Project? The two atomic bombs were different. They used different fuel-different elements!"

Soshi clapped her hands. "Yes! He’s right! I read that! The two bombs used different fuels! One used uranium and one used plutonium! Two different elements!"

A hush swept across the room.

"Uranium and plutonium!" Jabba exclaimed, suddenly hopeful. "The clue asks for the difference between the two elements!" He spun to his army of workers. "The difference between uranium and plutonium! Who knows what it is?"

Blank stares all around.

"Come on!" Jabba said. "Didn’t you kids go to college? Somebody! Anybody! I need the difference between plutonium and uranium!"

No response.

Susan turned to Soshi. "I need access to the Web. Is there a browser here?"

Soshi nodded. "Netscape’s sweetest."

Susan grabbed her hand. "Come on. We’re going surfing."

Chapter 125

"How much time?" Jabba demanded from the podium.

There was no response from the technicians in the back. They stood riveted, staring up at the VR. The final shield was getting dangerously thin.

Nearby, Susan and Soshi pored over the results of their Web search. "Outlaw Labs?" Susan asked. "Who are they?"

Soshi shrugged. "You want me to open it?"

"Damn right," she said. "Six hundred forty-seven text references to uranium, plutonium, and atomic bombs. Sounds like our best bet."

Soshi opened the link. A disclaimer appeared.

The information contained in this file is strictly for academic use only. Any layperson attempting to construct any of the devices described runs the risk of radiation poisoning and/or self-explosion.

"Self-explosion?" Soshi said. "Jesus."

"Search it," Fontaine snapped over his shoulder. "Let’s see what we’ve got."

Soshi plowed into the document. She scrolled past a recipe for urea nitrate, an explosive ten times more powerful than dynamite. The information rolled by like a recipe for butterscotch brownies.

"Plutonium and uranium," Jabba repeated. "Let’s focus."

"Go back," Susan ordered. "The document’s too big. Find the table of contents."

Soshi scrolled backward until she found it.

I. Mechanism of an Atomic Bomb

A) Altimeter

B) Air Pressure Detonator

C) Detonating Heads

D) Explosive Charges

E) Neutron Deflector

F) Uranium Plutonium

G) Lead Shield

H) Fuses

II. Nuclear Fission/Nuclear Fusion

A) Fission (A-Bomb) Fusion (H-Bomb)

B) U-235, U-238, and Plutonium

III. History of the Atomic Weapons

A) Development (The Manhattan Project)

B) Detonation 1) Hiroshima 2) Nagasaki 3) By-products of Atomic Detonations 4) Blast Zones "Section two!" Susan cried. "Uranium and plutonium! Go!"

Everyone waited while Soshi found the right section. "This is it," she said. "Hold on." She quickly scanned the data. "There’s a lot of information here. A whole chart. How do we know which difference we’re looking for? One occurs naturally, one is man-made. Plutonium was first discovered by-"

"A number," Jabba reminded. "We need a number."

Susan reread Tankado’s message. The prime difference between the elements… the difference between… we need a number… "Wait!" she said. "The word ‘difference’ has multiple meanings. We need a number-so we’re talking math. It’s another of Tankado’s word games-‘difference’ means subtraction."

"Yes!" Becker agreed from the screen overhead. "Maybe the elements have different numbers of protons or something? If you subtract-"

"He’s right!" Jabba said, turning to Soshi. "Are there any numbers on that chart? Proton counts? Half-lives? Anything we can subtract?"

"Three minutes!" a technician called.

"How about supercritical mass?" Soshi ventured. "It says the supercritical mass for plutonium is 35.2 pounds."

"Yes!" Jabba said. "Check uranium! What’s the supercritical mass of uranium?"

Soshi searched. "Um… 110 pounds."

"One hundred ten?" Jabba looked suddenly hopeful. "What’s 35.2 from 110?"

"Seventy-four point eight," Susan snapped. "But I don’t think-"

"Out of my way," Jabba commanded, plowing toward the keyboard. "That’s got to be the kill-code! The difference between their critical masses! Seventy-four point eight!"

"Hold on," Susan said, peering over Soshi’s shoulder. "There’s more here. Atomic weights. Neutron counts. Extraction techniques." She skimmed the chart. "Uranium splits into barium and krypton; plutonium does something else. Uranium has 92 protons and 146 neutrons, but-"

"We need the most obvious difference," Midge chimed in. "The clue reads ‘the primary difference between the elements.’ "

"Jesus Christ!" Jabba swore. "How do we know what Tankado considered the primary difference?"

David interrupted. "Actually, the clue reads prime, not primary."

The word hit Susan right between the eyes. "Prime!" she exclaimed. "Prime!" She spun to Jabba. "The kill-code is a prime number! Think about it! It makes perfect sense!"

Jabba instantly knew Susan was right. Ensei Tankado had built his career on prime numbers. Primes were the fundamental building blocks of all encryption algorithms-unique values that had no factors other than one and themselves. Primes worked well in code writing because they were impossible for computers to guess using typical number-tree factoring.

Soshi jumped in. "Yes! It’s perfect! Primes are essential to Japanese culture! Haiku uses primes. Three lines and syllable counts of five, seven, five. All primes. The temples of Kyoto all have-"

"Enough!" Jabba said. "Even if the kill-code is a prime, so what! There are endless possibilities!"