“Yes,” said Diane.
“OK, so it’s not modern. No computer to help him with it. Maybe it’s something popular among coders of his time, like Vigenere’s method,” said Frank. “Where, for example, the cipher letter for e in one word isn’t necessarily the same cipher letter for an e in another word.”
“Well, you’ve completely lost me,” said Neva.
“Wow,” said Jin, leaning forward, his eyes now sparkling with interest. “No wonder I couldn’t decipher it. How do you know about this stuff, Frank?”
“It’s only what he does for a living,” said David.
“No kidding. I didn’t know that’s what you do,” said Jin.
“It’s part of what I do,” said Frank. “A lot of cybercrime involves hiding things by use of encryption.”
“Can you decipher it?” Diane asked.
“Probably. It will be easier if I have the keyword,” he said.
“Keyword?” they all said in unison.
“Several of the early ciphers required a keyword. Even without the keyword, there are other ways it can be deciphered and a good computer program can work it out, but if I have the keyword, I can do it fairly quickly. Are there any possible keywords from this story of yours?”
“How about a key sentence?” said Diane. “The making of palimpsests was possible even with papyri.”
Frank raised his eyebrows and she explained about the amazing coincidence of hearing that phrase in the library, Juliet’s fear of the word palimpsest and her dramatic reaction to hearing the complete sentence.
“Well that’s certainly odd,” said Frank.
David, Neva, and Jin stared at her with their mouths open.
“Wow,” said Jin again. “We hadn’t heard that story, Boss.”
“There’s been so much going on lately,” Diane said. She turned back to Frank. “Do you think palimpsest could be the keyword?”
“Could be. I’ll give it a try. Can I use a computer?” said Frank. “You do have word processing programs on your computers, don’t you?”
“Of course,” said David.
He led Frank to his computer and called up Word-Perfect. Frank sat down and started typing.
David moved an empty chair next to Frank, and Diane sat down. She was feeling a little weak, and her headache was back, but she didn’t want to mention it. David probably guessed, she thought. Frank reached over and squeezed her hand. He probably senses my weakness too, damn it.
Frank made a grid twenty-seven by twenty-six. On the top row he keyed in each letter of the alphabet in lowercase. Under the a in the first column, he repeated the alphabet starting with an uppercase B and putting the uppercase A on the bottom of the column after Z. He did the same thing in the next column-under the lowercase b he put an uppercase C and put the uppercase A and B at the bottom of the column after Z. Each successive uppercase alphabet was shifted one letter with respect to the previous column.
“This is called a Vigenere square,” said Frank when he finished. “The lowercase letters across the top represent the plain text. The uppercase letters in the columns represent the cipher text.”
Neva made a gesture with her hand going over her head. “This looks too much like math with letters,” said Neva.
“Not far from wrong,” said Frank.
“This is great,” said Jin. “Where have I been that I didn’t know this?”
“I don’t know,” said Frank grinning. “This is Secret Code 101.”
“How does it work?” said Diane.
“Let’s say the keyword is DIANE. In the left column I will use only those letters.” He used the word processing program to highlight the letters of DIANE and continued the shading all across the row in the table for each letter.
“Now, suppose we have the message, ‘The house that Jack built.’ So, we have to make another table…,” began Frank.
“OK,” said Neva. “You mentioned something about a computer program that would do this?”
“Yes, but I don’t have it,” said Frank. “Let’s have a little patience. Think of this as fun. Jin does.”
“You betcha,” said Jin. He pulled up a chair and leaned forward, staring at the screen. “You said you use a second table?”
“Yes,” said Frank. “If the keyword is DIANE, on the header row of this table I write the word DIANE over and over again until I have used up all the letters in the message to be encoded.
“Oh, I get it.” Jin jumped up and sat down again. “That’s brilliant. No wonder I couldn’t make heads or tails of it.”
“Explain it to those of us who don’t get it,” said Neva.
“To encrypt ‘The house that Jack built,’ ” said Frank, “I go to the new table and see that the first letter in the message is t and it is under the letter D in the keyword DIANE. I go to the Vigenere square and use it like the coordinates of a map to find the encryption letter I need. Go to D on the left most column and find where it intersects with t in the top row. The letter where the column and row intersect is W. Do the same thing for the second letter. The h is under I in the keyword Diane. Go to the square and we find that I and h intersect at P. Keep going and you can encrypt the whole sentence. You do the reverse process to decode the message.”
“That is so cool,” said Jin. “You’ll have to show me how to decode it the other ways you were talking about.”
“Sure. It’s more time-consuming. As you see, if you have the keyword, it’s a piece of cake.”
“Yeah,” said David, “I’d like to see the computer program. That would be an interesting algorithm.”
“How about our message?” said Diane.
“OK, we’re hoping the keyword is palimpsest.” Frank took the first word in the doll code and tried it out with his square. KVQ = vvf. “Palimpsest isn’t the keyword,” he said.
“Try papyri,” said Diane.
“Won’t work,” said Frank. “Papyri and palimpsest start out with the same two letters. We’ll end up with vv again.”
“So we’re nowhere,” said Neva.
“Or an alternative method for decoding it,” said Jin.
“Maybe the keyword is his name,” said Neva.
“That would be too easy to decode,” said Jin. “If you are going to the trouble to have an elaborate code, you won’t have such an easy keyword.”
The phone rang and Diane answered. She was expecting Garnett, but it was Beth, the museum’s librarian.
“Beth,” said Diane. “You have something for me?”
“Yes, I do. I can bring it to you. I thought you’d like to know that I did find some descendants of Leo Parrish that you might be able to contact. I don’t know where they are now, but I have info on the last-known locations of some of them.”
“Great. Can you come to the crime lab?” Diane asked.
“Yes. I’ll walk right over,” said Beth.
Diane explained to the others that she’d enlisted the help of a genealogist to discover any relatives of Leo Parrish.
“That was clever,” said Frank.
“And fast,” said Diane. “Librarians are much speedier than private detectives.”
It took only a couple of minutes for Beth to cross from the third-floor east wing to the west wing where the crime lab was. David was at the door to let her in. She entered, looking around at all the glass walls and high-tech equipment as though she’d just stepped onto another planet.