The History and Mathematics of Codes and Code Breaking

Tag: Vignère cipher

Needle in a Haystack

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.

Is Communication Ever Secure?

Before the telegraph was invented and introduced to society, the only way of sending messages was through written means. If you wanted to send a message to a receiver that lived far away, you needed a middleman – someone to transport the message. The telegraph effectively removed the worry that your message would be intercepted or stolen along the way. Although you knew that the message was being sent to the correct machine, however, you didn’t know that it was reaching its intended receiver in its correct form.  You had to trust that the telegraph operator would be honest and secretive in translating/delivering the message. There was essentially no way of confirming that the correct person was at the other end of the receiver. Additionally, some people wanted to send messages that they were uncomfortable with others reading at all. This led to the encryption of messages even before being given to the operator. The desire to keep messages secret from the sender and protect the message in case it didn’t reach its intended receiver have motivated the use of a more secure cipher, the Vignère cipher. This cipher, more complicated than the monoalphabetic cipher, remained the standard for many years. 

After the telegraph, the telephone was invented. At first, though, the telephone still didn’t allow for direct, secure communication. There were telephone operators that would connect calls, and they could potentially listen in on calls without the either line knowing. However, calls became more secure with the invention of the rotary dial. And now, we communicate through talk, text, or email, typically through our smartphones. Nowadays, most people communicate primarily through text or email, not over the phone. Our communications are surely much more secure now than they were years, even decades ago, but I worry that our messages are never truly secure. There are always ways that companies, hackers, or the government can access anything that travels via the web. The only form of truly secure communication is face-to-face. 

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