Digital Fortress

'So what?'

David leaned toward the camera. His face filled the frame. 'Sixty-four letters…'

Susan nodded. 'Yes, but they're-' Susan froze.

'Sixty-four letters,' David repeated.

Susan gasped. 'Oh my God! David, you're a genius!'

Chapter 121

'Seven minutes!' a technician called out.

'Eight rows of eight!' Susan shouted, excited.

Soshi typed. Fontaine looked on silently. The second to last shield was growing thin.

'Sixty-four letters!' Susan was in control. 'It's a perfect square!'

'Perfect square?' Jabba demanded. 'So what?'

Ten seconds later Soshi had rearranged the seemingly random letters on the screen. They were now in eight rows of eight. Jabba studied the letters and threw up his hands in despair. The new layout was no more revealing than the original.

P F E E S E S N

R E T M P F H A

I R W E O O I G

M E E N N R M A

E N E T S H A S

D C N S I I A A

I E E R B R N K

F B L E L O D I

'Clear as shit.' Jabba groaned.

'Ms. Fletcher,' Fontaine demanded, 'explain yourself.' All eyes turned to Susan.

Susan was staring up at the block of text. Gradually she began nodding, then broke into a wide smile. 'David, I'll be damned!'

Everyone on the podium exchanged baffled looks.

David winked at the tiny image of Susan Fletcher on the screen before him. 'Sixty-four letters. Julius Caesar strikes again.'

Midge looked lost. 'What are you talking about?'

'Caesar box.' Susan beamed. 'Read top to bottom. Tankado's sending us a message.'

Chapter 122

'Six minutes!' a technician called out.

Susan shouted orders. 'Retype top to bottom! Read down, not across!'

Soshi furiously moved down the columns, retyping the text.

'Julius Caesar sent codes this way!' Susan blurted. 'His letter count was always a perfect square!'

'Done!' Soshi yelled.

Everyone looked up at the newly arranged, single line of text on the wall-screen.

'Still garbage,' Jabba scoffed in disgust. 'Look at it. It's totally random bits of-' The words lodged in his throat. His eyes widened to saucers. 'Oh… oh my…'

Fontaine had seen it too. He arched his eyebrows, obviously impressed.

Midge and Brinkerhoff both cooed in unison. 'Holy… shit.'

The sixty-four letters now read:

PRIMEDIFFERENCEBETWEENELEMENTSRESPON

SIBLEFORHIROSHIMAANDNAGASAK I

'Put in the spaces,' Susan ordered. 'We've got a puzzle to solve.'

Chapter 123

An ashen technician ran to the podium. 'Tunnel block's about to go!'

Jabba turned to the VR onscreen. The attackers surged forward, only a whisker away from their assault on the fifth and final wall. The databank was running out of time.

Susan blocked out the chaos around her. She read Tankado's bizarre message over and over.

PRIME DIFFERENCE BETWEEN ELEMENTS RESPONSIBLE FOR HIROSHIMA AND NAGASAKI

'It's not even a question!' Brinkerhoff cried. 'How can it have an answer?'

'We need a number,' Jabba reminded. 'The kill-code is numeric.'

'Silence,' Fontaine said evenly. He turned and addressed Susan. 'Ms. Fletcher, you've gotten us this far. I need your best guess.'

Susan took a deep breath. 'The kill-code entry field accepts numerics only. My guess is that this is some sort of clue as to the correct number. The text mentions Hiroshima and Nagasaki-the two cities that were hit by atomic bombs. Maybe the kill-code is related to the number of casualties, the estimated dollars of damage…' She paused a moment, rereading the clue. 'The word 'difference' seems important. The prime difference between Nagasaki and Hiroshima. Apparently Tankado felt the two incidents differed somehow.'

Fontaine's expression did not change. Nonetheless, hope was fading fast. It seemed the political backdrops surrounding the two most devastating blasts in history needed to be analyzed, compared, and translated into some magic number… and all within the next five minutes.

Chapter 124

'Final shield under attack!'

On the VR, the PEM authorization programming was now being consumed. Black, penetrating lines engulfed the final protective shield and began forcing their way toward its core.

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