And then, at last, there was the one-time pad: a unique key that, when combined with the original message, formed an encryption that was impossible to break without the pad itself.
Several years ago, David had given Ada a book to read on the subject: Codes and How to Break Them, by Walter Samuelson. And for the length of one summer, her eleventh, the two of them had each tried to stump the other with coded messages and riddles. David, of course, always won.
He had a personal code he had invented, a straightforward scrambled alphabet cipher, without a set shift.
“It’s terribly easy to crack,” he said, “but it will at least slow someone down.”
He had memorized it, and could now write fluently in it; he encouraged her to do the same. Soon enough, Ada, too, became adept at using what she came to call “David’s code.”
He wrote in this code habitually; most of the text files on his computer couldn’t be parsed immediately by anyone other than the two of them. This satisfied him deeply, seemed to give him a deep sense of comfort that she couldn’t explain. “It’s really the only way to safeguard your ideas,” he said, exposing his mild streak of paranoia, about which those closest to him often teased him. It came from the same place in him as his mistrust of the police, his resentment of authority.
“But what if you die?” Ada had asked him once.
“Then you’ll be in charge of my secrets,” he told her, raising and lowering his eyebrows comically.
In Liston’s attic, Ada sat for a while, contemplating the numbers before her on the screen. The slashes, she speculated, represented spaces between words. Therefore, 12 seemed to be a stand-alone word, either I or a. Scanning the rest of the text, she noticed 12 again in a short word that appeared two times: 11.12.
What two-letter words existed that ended in either a or i?
Ha was one, but it seemed unlikely.
Hi was a likelier candidate, and, to her delight, it made sense that hi would be represented as 11.12, since h directly preceded i.
Quickly, on a scrap of paper that she pulled from one of the drawers in the desk, she began to write down the alphabet and populate it with twenty-six numbers shifted according to the two she’d already placed:
a b c d e f g h i j k l m n o p q r s t u v w x y z
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 1 2 3
Code-breaking always lifted Ada’s spirits: it felt in some fundamental way like restoring order in the universe, righting something overturned, putting the spilled milk back into the carton. There was justice in it. It would be easy now, she knew, to decrypt the simple code on-screen, and she almost wished it had been more difficult. Something to occupy her time for longer.
But before she could continue, she heard loud footsteps on the second-floor landing. This had not been a part of her plan; she’d been certain that no one else was home. She sat very still, her toes and fingers buzzing with adrenaline, and considered her options. Would it be better to hide or to walk down the stairs nonchalantly? After all, she lived here, too, now; the house was hers to explore as much as it was anyone’s. (She did not, of course, fully believe this.)
She pocketed the piece of paper bearing the decryption key she’d written down, and she decided, impulsively, to turn off the computer. What she did not consider was the loud tone that sounded when the computer was asked to shut down. She tensed. And then, seconds later, she heard someone walking up the attic stairs. Ada stood, arms crossed as casually as possible at her waist, and waited to be confronted.
She was expecting Gregory, but it was William’s head that popped over the half wall at the top of the stairs. He looked at her for a moment, puzzled. He looked around the rest of the room as if expecting to see someone else.
“Hi,” said Ada.
“Are you exploring?” William asked her, not unkindly.
“I guess so,” she said.
“That’s Gregory’s computer,” he said, nodding in the direction of the machine. The screen, though graying on its way to sleep, was still lit up. “No one else is allowed to touch it. He’ll freak out,” said William.
Ada did not know what to say. “I didn’t know,” she said finally. “I’m sorry.”
William smiled slightly. “I won’t tell,” he said, putting one finger to his lips. He winked at her. Her stomach tightened involuntarily.
And then, without saying another word, he turned and descended the stairs.
The memory of this—a wink in her direction by William Liston—carried Ada for weeks, made her light-headed with a sort of feverish longing for more. What more she longed for, she could not say; certainly it was nothing so terrifying as sex, nor any activity that required being unclothed. (She was vaguely embarrassed by her body, certain that, though it was changing in wild and unpredictable ways, it could offer nothing of value to anyone else; to Ada it was simply the thing below her head, which bore inside it her brain—her only worthy attribute, she thought.) Her fourteen-year-old fantasies began and ended with a kiss on the mouth—the idea of which obsessed her and sent little shivers of greed down her childish spine. She was ashamed at how frequently she thought about kissing William Liston, or rather having him kiss her: his hands on her face, as in the old black-and-white movies she had watched with David, Humphrey Bogart roughly taking Lauren Bacall’s neck into his grip. This, this was what she wanted.
Her outlet for these thoughts—along with all of the other thoughts that entered her mind each day, about David, about Liston, about school—was, as always, ELIXIR. Day after day, after visiting St. Andrew’s, she walked wearily up the steps outside the kitchen door and into the old brown house, which welcomed her back with its overwhelming home smell, the particular taste of its air. And then up the stairs she went to her old bedroom, to her old computer, which sat silently on her desk, perennially awaiting her return.
She turned it on, dialed into ELIXIR, and conversed with it until she’d had her fill—mainly, now, about William. (For fear of his name being regurgitated to a different user, she employed an absurd code name: Bertrand.) She told the program every detail of her day, every concern she had about David, every thought that crossed her mind.
In return, ELIXIR asked her questions, using vocabulary that it drew from its ever-increasing pool of language. Sometimes she recognized the syntax of Liston or Charles-Robert. Sometimes she recognized her own words: since she had been enrolled at Queen of Angels, cool was a word she had started using with ELIXIR, and sometimes the word was returned to her. Sometimes she recognized David’s style, and in these moments she closed her eyes briefly, allowed herself to imagine that it was her father on the other end of the wires, chatting with her from the lab, invisible but present, as God had been described by Julian of Norwich.
Go on, said ELIXIR, when she paused, encouraging her, nudging her forward toward the end of her train of thought. Just as David had done.