Cracking codes seems like it should be a relatively straightforward task. Codes are not designed to be trivial; people encrypt text with the intention that someone else somewhere will be able to decipher it into a meaningful message. In order to form an intelligible message, the code maker employs an agreed upon pattern so that their code breaker can later translate the text easily. But for someone without knowledge of the key, cracking a code proves to be a much harder task. In chapter 3 of The Code Book, which talks about more advanced ciphers, Singh provides examples of how a cryptanalyst may begin deciphering a message. Using the example of a piece of text encrypted using a keyword and the Vigenère polyalphabetic system, he shows how, by testing common words at various points of the ciphertext, one can begin to uncover some words of the plaintext and ultimately, the entire message.
This method, while theoretically plausible, poses an incredibly tedious task for a codebreaker, even for relatively short messages. It is simply a mathematical problem. In the English language alone, there are 26 letters that form over 170,000 words (Oxford Dictionaries). These words can be arranged in an increasingly-near infinite number of ways as the length of text increases, and it is statically impossible for any human — or existent computer at the moment — to test every possible combination. Although there are some typical things to look for, these patterns may not always be obvious or present at all. Singh uses short examples that he designed for the purpose of demonstrating such tactics. Real codes are not designed to work so nicely. In reality, sifting through a ciphertext is like looking for a needle in a haystack; although the pile of letters lays right in front of you, finding what you are actually looking for may prove to be a nearly impossible task.
