One late afternoon, after her return from St. Andrew’s, and on a rare occasion when nobody was home, Ada decided impulsively that she wanted to see Gregory’s lair for herself. She opened the door on the upstairs hallway that led to the attic stairs and took them quickly, two at a time. The central air did not extend to the third floor, and she instantly noticed the change in temperature, which felt more familiar to her: more like the home she had shared with David. It smelled familiar to her, too—dusty and mildewed and bookish.
A half wall that ran along the top of the staircase obscured the room until she reached the final step, at which point she looked over it, into the large room. It was decorated in a totally different style than the rest of the house. Liston had said dismissively that it used to be storage, and several tall piles of boxes and equipment still occupied one quarter of the space. The rest looked something like what was often called a rec room at that time. The ceiling slanted inward on either side to meet in a peak at the top. Liston’s ex-husband had partially, haphazardly finished it in the 1970s, and it bore the hallmarks of that decade’s style: bright orange shag carpeting nailed imperfectly onto the wooden floorboards, and faux-wood paneling covering the wall at either end of the room (or, in one place, leaning against it at an angle), and framed and unframed posters of seemingly arbitrary events and people and places. An enlarged photograph of a boxing match in Madrid in 1955. Reproductions of the original advertisements for North by Northwest and Taxi Driver and Charlton Heston in The Ten Commandments. A gaudy image of the Virgin Mary, her vivid red heart shooting rays of yellow light out of its center, extending her hands to the viewer and looking downward modestly. Liston’s ex-husband, Liston had told Ada, was devoutly religious, although, unlike his wife, he never went to church. Liston talked about him amiably, casually, as if she had long ago stopped caring about him; her sons, however, bore their wounds someplace deeper, and never spoke of him. Though he only lived two hours away in New Hampshire, they only saw him on Christmas and, on the rare occasions that he followed through, on their birthdays. Ada had never met him.
The furniture in the attic was old and worn. Here were two green, flowered couches, tattered, their stuffing falling out; a mismatched ottoman; a coffee table painted purple. There was one small window at each end of the attic and a third set into an eave, and they let in a dusty, comfortable light that Ada felt somehow that she could smell. In front of the eaved window was a desk, and atop the desk, to Ada’s surprise, was a personal computer: the same 128K Macintosh that David had sent home with every member of the lab, to further their work on ELIXIR. The same model that Ada had in her bedroom, and on which she chatted in secret, almost every afternoon, with the program. Since then, newer machines had been purchased, and were in use. This one, presumably, had been donated by Liston to her sons when the 512K became available.
Ada walked toward it.
There was a moment of hesitation; her hand physically paused on its way toward the little toggled switch that woke the machine. She touched the top of it first, patting it gently, running a hand over it, as one might touch the head of a dog. Then, listening intently for a moment, she determined that no one had yet returned to the house. She calculated that she would have just enough time to shut it down if she did so the moment the front door opened. She’d shut it down, she thought, and then run quietly, quickly, to the bottom of the attic stairs and back into her room.
She switched it on. A deep flush came over her face; her heart beat more quickly. First there was the whir of whatever disk occupied its disk drive, and then the screen lit up, displaying the smiling computer icon—content, it always seemed to her, because its belly was full of data.
There was a metal folding chair facing the computer, and while the machine booted up she perched on the edge of it nervously, alert, waiting for sounds in the house.
When, at last, the machine was awake, Ada saw that the name of the disk was Dontlook12, and, after a moment of deep, shameful self-interrogation, she opened it anyway. She was an ethical child in many ways, but the temptation was too great.
The folder revealed a series of text documents titled, simply, One, Two, Three. The last one was titled Fiftyfive, and it had last been opened the day before. She double-clicked on the name. When it appeared, it looked at first to be corrupted: she found nothing but a series of numbers separated by periods and slashes.
2.8.22.23.8.21.7.4.2 4.7.4 22.4.12.7 11.12 23.18 16.8 4.17.7 12 22.4.12.7 11.12 23.18.18
She had seen this before: text files so corrupt that they looked like gibberish. But this one looked different. No punctuation marks populated it, for one thing; normally, corrupt files looked like a list of cartoonish substitutes for curse words (often reflecting the feelings of the user), ampersands and asterisks strung together like pearls.
This, she thought with some excitement, looked more like code.
David had always been interested in codes: he viewed them as thinking exercises, puzzles that he created and asked Ada to solve. The simplest code, the one he started her on as soon as she could read and write and count, was numerical substitution, an easy back-and-forth between letters and numbers, like so:
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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
This encryption key was the first one Ada memorized, and now it came so easily to her that she could almost think in it, could spell out words and sentences in numbers as easily as letters. Variations on this most basic key abounded. The numerical substitutions for letters could, for example, be shifted by x places, so that a no longer corresponded to 1, like so:
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
18 19 20 21 22 23 24 25 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
A more difficult code to crack could be achieved if numerical substitutions were chosen randomly and then used uniformly, thus:
a b c d
17 2 5 12
and so on.
When breaking a code like the last one, the decoder would have to rely on the lengths of common words for cracks in the code—words like I and a, which would appear as stand-alone numbers and act as a good starting point for the tedious work of deciphering everything else. This loophole, however, could be easily eliminated if the words were run together with no spaces in between. Then the decoder would have to hope that he or she had an excerpt of such substantial length that the frequency with which certain letters occur in the English language could be taken into consideration.
A fourth, considerably more difficult variant on number substitution involved machine-encoded text, a sort of polyalphabetic code in which each letter had no permanent, standard substitute. The machines would instead disguise each letter differently at various points in the text, using either mechanical or electronic hardware to execute the task. Only a decoding machine programmed as an exact mirror of the encoder could untangle the knot of words.