Humour

Cryptic conversations

T A Balasubramanian on the fascinating history of encryption.

“Well, since you two seem to have had more than your fill with my talk about tomatoes, let me call upon my specialist in putting things into code,” says Gyani Billmemore. The half-owner of the firm Gyani Billmemore & Sellmemore (known in business circles as GBS), is determined to keep up the tempo.

The Gyani’s expansive lecture on disposable computers has given you, Papyrus Bytewala, CIO of Baffle Corporation, an overdose of techno-hype, caught up as you are presently at the Techno Over-exposition of Geeks and Gizmos for Lazy Enterprises (TOGGLE). And it has even managed to nettle your intrepid CTO, Danny DeVito, the first biped walking humanoid.

So Gyani, the “Guru of Gizmotopia,” flamboyantly attired in a bulky flowing gown that seems to mark him as an all-knowing Indian sage, finally gets the message, as he introduces a pretty lady with a hint of a smile. “Meet Prima Donna, who has created a revolution in security with her wonderful encryption devices.”

“Encryption? Now that is something I would like to hear more about,” says DeVito, with a new gleam in his eyes, sparked, no doubt, by the prospect of exchanging talk with a beautiful human in female form.

“Oh, gentlemen, it is my pleasure to meet you,” coos Donna, shaking hands coyly and tossing her dark hair sideways.

“We are all ears, Ms Donna,” says DeVito, pointing to his ears with unnecessary zeal.

“Encryption is one of those words in the contemporary lexicon that is freely tossed about to describe something that is part mystery and part act of faith,” Donna says softly. “But to study the history of encryption is to enter a world of intrigue, espionage, and mathematical wizardry.”

“Oh my,” you mutter. “This is where Danny should get his drama school education updated.”

You wonder if this return to cheerful social interaction is indication that your humanoid friend has been programmed to respond to the opposite sex with enthusiasm beyond the minimum required in polite conversation.

“For thousands of years, people have found it necessary to disguise their secrets. And for an equal number of years, those with patience and skill have found ways of deciphering hidden messages. Encryption is almost as old as secrets, and its evolution is superbly chronicled in my book—The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography.”

“Ancient Egypt, indeed,” says DeVito, hands folded behind him.

“The earliest techniques for sending confidential messages were more a matter of cleverness than coding. The Greek historian Herodotus talks of a messenger’s head that was shaved and the message written on his scalp. The sender then patiently waited for the messenger’s hair to regrow before he dispatched him with the missive. This was, clearly a period of history that tolerated a certain lack of urgency.”

“Yes, of course. No one was in a hairy,” says DeVito, pointing to his own bald pate. Donna frowns, then laughs as she gets the pun. This is a revelation to you—here was DeVito exhibiting a subtle sense of humour.

“Yes, Mr DeVito. But hiding a message, no matter how adroitly, leaves the sender vulnerable to discovery or betrayal. Cryptography was developed to disguise not the existence but the meaning of a message so that even if it were intercepted, it cannot be understood.”

“That is something James Bond would love,” says DeVito.

“When I disguise a message, I can use one of two common ploys: transposition or substitution. Transposition would mean rearranging the order of the letters that make a message. Its virtue is simplicity, and it gives me a staggering amount of possible encryption choices, even for a very short message. For example, the message ‘Meet Rita at the train station at midnight’ contains only 35 letters, but, if you count, you get 50 billion trillion trillion distinct rearrangements of them. The world’s entire population working day and night would require more than a thousand times the lifetime of the universe to check all the arrangements.”

DeVito lets out a soft whistle. “Ooh. That long?”

Donna smiles at him. “That, of course, was before computers significantly shortened the task. With substitution, I may replace each letter of a text with a different letter, so that ‘meet Rita’ may look like ‘pggv Ulvd’. If I jumble the letters of the alphabet, I can create a cipher text of even greater variety than transposition. But since certain letters are used more often than others, educated guesses can be made by clever code-breakers, noting the frequency and positioning of characters. Now if I use transposition and substitution in tandem, however, they make a deadly cipher.”

“Well, let me get you back a little way,” you say, patiently. “Why do we need all this secret coding?”

“Good question, Mr Papyrus, even if it comes from a CIO,” says Donna, waving a slender hand, “Cryptography was originally the stuff of spooks and diplomats, but it is now getting more important because these days, it’s nearly impossible to keep a computer off the public networks, and even if you could, there is always a chance a document might leak out on somebody’s USB memory stick. With some cryptography, you can keep files in their encrypted form and give out the decryption key only to the right guys.”

“Sounds easy,” says DeVito. “Unless, of course, there are evil code-breakers who are as good as the code-makers.”

“Ah, there you have it, Mr DeVito,” says Donna, smiling and patting the humanoid. “The code-breakers are all out there, using their twisted little brains to try and break even the most complicated encryption schemes.”

“How complicated can it be?” you ask, sceptically.

“Well, it is like mixing a bowl of wet cement,” says Donna. “Take the Data Encryption Standard (DES) that IBM dreamed up. It caused a great uproar in security agencies. Here is how it works. First, your message is turned into a long string of binary digits. Then, the string is split into blocks of 64 digits, and encryption is performed separately on each of the blocks. Third, focusing on just one block, the 64 digits are shuffled, and then split into two half-blocks of 32, labelled Left-0 and Right-0. Follow me so far?”

“Right-0,” says DeVito. “But I’m not sure.”

“Now the digits in Right-0 are then put through a ‘mangler function’ which changes the digits according to a complex substitution. The mangled Right-0 is then added to Left-0 to create a new half-block of 32 digits called Right-1. The original Right-0 is relabelled Left-1. This set of operations is called a ‘round’. Clear so far?”

“I think my eyes are getting crossed,” says DeVito, who has been attempting to follow the process by waving his two hands around.

“That’s all,” says Donna. “Then this entire sequence is repeated until there have been 16 rounds in total. Simple?”

“Oh, it is child’s play,” you say, nodding grandly.

“But the royal war between code-makers and code-breakers is heading toward a climax,” says Donna, with a sigh. “In the near future, we may reach an impasse where no prior encryption would be unbreakable and all future encryption would be absolutely undecipherable. Soon, a quantum computer will be capable of massive, nearly instantaneous parallel processing, and no cipher would be complex enough to confound it. And to encrypt messages, quantum computers would use polarized photons, whose behaviour is unpredictable and therefore impossible to divine.”

“Far simpler to let sleeping secrets lie,” says DeVito, cryptically.

“Who would want to take on cracking photons?”