As Singh deciphered the example of the Vigènere cipher on page 116, and also other ciphers previously, I contemplated just how simple he was making them. He makes a lot of assumptions, and he also never points out some flaws that I have seen in his messages. In the example on page 16, Singh uses a message that makes his technique work very well. In this example, he uses a keyphrase that is as long as the message. Normally, this should be almost impossible to crack, because none of the cipher alphabets would be repeated in a pattern. He proposes a solution, by placing common words (he uses “the”) in random locations in the plaintext. In his example, he gets it right on the first try. This is not that unlikely with such a short message, but a full paragraph of a long letter would take many more tries. He also makes the assumption that the cryptographer encrypting the message would use the word “the”, or “and”, or whatever word. If a cryptographer knew their code could be broken that way, they could simply refrain from using common words often. Once there are fewer common words present, it becomes much more difficult to crack. In addition, using the method he proposed can cause false positives. It’s possible that the letters “the” in the plaintext produce a discernible string of three letters in the ciphertext. If the cryptographer was smart, they could place a few traps, so that random keywords would show up in the cipher text. This would completely confuse the person deciphering the code, and may just make it extremely difficult to crack. Singh fails to address these flaws in his examples, and it makes it cryptanalysis seem easier than it really is.
Leave a Reply