NDAKOTA@ara.anon.org It was the letters ARA in the address that had caught Susan’s eye. ARA stood for American Remailers Anonymous, a well‑known anonymous server.

Anonymous servers were popular among Internet users who wanted to keep their identities secret. For a fee, these companies protected an E‑mailer’s privacy by acting as a middleman for electronic mail. It was like having a numbered post office box‑a user could send and receive mail without ever revealing his true address or name. The company received E‑mail addressed to aliases and then forwarded it to the client’s real account. The remailing company was bound by contract never to reveal the identity or location of its real users.

“It’s not proof,” Strathmore said. “But it’s pretty suspicious.”

Susan nodded, suddenly more convinced. “So you’re saying Tankado didn’t care if anybody searched for North Dakota because his identity and location are protected by ARA.”

“Exactly.”

Susan schemed for a moment. “ARA services mainly U.S. accounts. You think North Dakota might be over here somewhere?”

Strathmore shrugged. “Could be. With an American partner, Tankado could keep the two pass‑keys separated geographically. Might be a smart move.”

Susan considered it. She doubted Tankado would have shared his pass‑key with anyone except a very close friend, and as she recalled, Ensei Tankado didn’t have many friends in the States.

“North Dakota,” she mused, her cryptological mind mulling over the possible meanings of the alias. “What does his E‑mail to Tankado sound like?”

“No idea. COMINT only caught Tankado’s outbound. At this point all we have on North Dakota is an anonymous address.”

Susan thought a minute. “Any chance it’s a decoy?”

Strathmore raised an eyebrow. “How so?”

“Tankado could be sending bogus E‑mail to a dead account in hopes we’d snoop it. We’d think he’s protected, and he’d never have to risk sharing his pass‑key. He could be working alone.”

Strathmore chuckled, impressed. “Tricky idea, except for one thing. He’s not using any of his usual home or business Internet accounts. He’s been dropping by Doshisha University and logging on to their mainframe. Apparently he’s got an account there that he’s managed to keep secret. It’s a very well‑hidden account, and I found it only by chance.” Strathmore paused. “So . . . if Tankado wanted us to snoop his mail, why would he use a secret account?”

Susan contemplated the question. “Maybe he used a secret account so you wouldn’t suspect a ploy? Maybe Tankado hid the account just deep enough that you’d stumble on to it and think you got lucky. It gives his E‑mail credibility.”

Strathmore chuckled. “You should have been a field agent. The idea’s a good one. Unfortunately, every letter Tankado sends gets a response. Tankado writes, his partner responds.”

Susan frowned. “Fair enough. So, you’re saying North Dakota’s for real.”

“Afraid so. And we’ve got to find him. And quietly. If he catches wind that we’re onto him, it’s all over.”

Susan now knew exactly why Strathmore had called her in. “Let me guess,” she said. “You want me to snoop ARA’s secure database and find North Dakota’s real identity?”

Strathmore gave her a tight smile. “Ms. Fletcher, you read my mind.”

When it came to discreet Internet searches, Susan Fletcher was the woman for the job. A year ago, a senior White House official had been receiving E‑mail threats from someone with an anonymous E‑mail address. The NSA had been asked to locate the individual. Although the NSA had the clout to demand the remailing company reveal the user’s identity, it opted for a more subtle method‑a “tracer.”

Susan had created, in effect, a directional beacon disguised as a piece of E‑mail. She could send it to the user’s phony address, and the remailing company, performing the duty for which it had been contracted, would forward it to the user’s real address. Once there, the program would record its Internet location and send word back to the NSA. Then the program would disintegrate without a trace. From that day on, as far as the NSA was concerned, anonymous remailers were nothing more than a minor annoyance.

“Can you find him?” Strathmore asked.

“Sure. Why did you wait so long to call me?”

“Actually"‑he frowned‑"I hadn’t planned on calling you at all. I didn’t want anyone else in the loop. I tried to send a copy of your tracer myself, but you wrote the damn thing in one of those new hybrid languages; I couldn’t get it to work. It kept returning nonsensical data. I finally had to bite the bullet and bring you in.”

Susan chuckled. Strathmore was a brilliant cryptographic programmer, but his repertoire was limited primarily to algorithmic work; the nuts and bolts of less lofty “secular” programming often escaped him. What was more, Susan had written her tracer in a new, crossbreed programming language called LIMBO; it was understandable that Strathmore had encountered problems. “I’ll take care of it.” She smiled, turning to leave. “I’ll be at my terminal.”

“Any idea on a time frame?”

Susan paused. “Well . . . it depends on how efficiently ARA forwards their mail. If he’s here in the States and uses something like AOL or CompuServe, I’ll snoop his credit card and get a billing address within the hour. If he’s with a university or corporation, it’ll take a little longer.” She smiled uneasily. “After that, the rest is up to you.”

Susan knew that “the rest” would be an NSA strike team, cutting power to the guy’s house and crashing through his windows with stun guns. The team would probably think it was on a drug bust. Strathmore would undoubtedly stride through the rubble himself and locate the sixty‑four‑character pass‑key. Then he would destroy it. Digital Fortress would languish forever on the Internet, locked for all eternity.

“Send the tracer carefully,” Strathmore urged. “If North Dakota sees we’re onto him, he’ll panic, and I’ll never get a team there before he disappears with the key.”

“Hit and run,” she assured. “The moment this thing finds his account, it’ll dissolve. He’ll never know we were there.”

The commander nodded tiredly. “Thanks.”

Susan gave him a soft smile. She was always amazed how even in the face of disaster Strathmore could muster a quiet calm. She was convinced it was this ability that had defined his career and lifted him to the upper echelons of power.

As Susan headed for the door, she took a long look down at TRANSLTR. The existence of an unbreakable algorithm was a concept she was still struggling to grasp. She prayed they’d find North Dakota in time.

“Make it quick,” Strathmore called, “and you’ll be in the Smoky Mountains by nightfall.”

Susan froze in her tracks. She knew she had never mentioned her trip to Strathmore. She wheeled. Is the NSA tapping my phone?

Strathmore smiled guiltily. “David told me about your trip this morning. He said you’d be pretty ticked about postponing it.”

Susan was lost. “You talked to David this morning?”

“Of course.” Strathmore seemed puzzled by Susan’s reaction. “I had to brief him.”

“Brief him?” she demanded. “For what?”

“For his trip. I sent David to Spain.”