Cryptography: The Key to Digital Security, How It Works, and Why It Matters by Keith Martin

Author:Keith Martin [Martin, Keith]
Language: eng
Format: epub
ISBN: 9781324004301
Google: oxe7DwAAQBAJ
Publisher: W. W. Norton & Company
Published: 2020-05-18T23:00:00+00:00

How to Save the World

Here’s cryptography in action, as often witnessed on television dramas (and the likes of James Bond movies).

Two intelligence agents sit tensely in a car, careering through busy city streets in a race against time. The driver is panicking and urgently talking to base. The passenger, the geeky agency computer analyst, has just inserted a recently purloined memory stick into a laptop computer. “What’s on there?” asks the driver. “It’s encrypted,” responds the analyst. “Can you break the code?” asks the driver. The analyst wrestles with the keypad while mysterious symbols dance across the screen, purses his lips, and slowly exhales. “I’ve never seen this means of encryption before; it’s unbelievably complex. Whoever wrote this knew what they were doing,” he says. “But can you crack it?” fires back the driver, as a timer on the screen hurtles second by second toward zero hour. The analyst grimaces and clatters his fingers over the keypad once more. The camera focuses on the laptop, where a digital Niagara of jumbled data is pouring down the screen. The driver runs a red light, overtakes a bus, and narrowly evades a head-on collision with a motorcycle. The analyst taps away at the keyboard, muttering to himself, eyes like saucers, staring in wonder at the festival of ciphertext on screen. The driver decides to take a shortcut and makes a sudden right turn, finding the way blocked by a garbage truck. The car screeches to a halt, and the driver sighs with despair as the timer enters the final seconds of its countdown. The analyst gasps, “I’ve got it!” And the world is saved, again.

Either the analyst has knowledge of an otherwise unknown unknown about cryptography, or (to get to the point of the issue as succinctly as possible) this is . . . nonsense.

What just happened? The cryptographic expert in the passenger seat reports that the encryption algorithm is unfamiliar. How did they work it out? Ciphertext from any decent encryption algorithm should appear to be randomly generated, so you shouldn’t normally be able to determine which algorithm was used to encrypt it just from idle inspection. But let’s set this problem aside. By somehow being able to deduce that none of the encryption algorithms he is familiar with have been used, the analyst is informing us that the algorithm is unknown to him. Since the analyst also indicates that whoever encrypted the data knew what they were doing, it is safe to assume the analyst has not extracted the decryption key from the memory stick (otherwise the key management is so poor that they certainly did not know what they were doing). So, the analyst knows neither the algorithm nor the key. Where, then, did the plaintext just come from?

There is only one conclusion. The analyst has, somehow, been able to try every possible algorithm and, for each of these algorithms, every possible key. Every possible algorithm? How many possible encryption algorithms could there be? It’s not even worth trying to reason about this; the number is so large that this capability can be safely dismissed.

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