Cryptography

The History and Mathematics of Codes and Code Breaking

Tag: communication

Not So Easy Anymore

In the previous chapter of The Code Book, Singh discussed cryptography during the time of Mary Queen of Scotts. During her time, cryptographers needed to be highly skilled and educated people who spent time dedicating themselves to the art of code breaking. The average person could not decipher encrypted messages. As I mentioned in an earlier blog post, the education level of the average person was very low. An educated person was one who was extremely privileged. Because of this, certain ciphers used during the time were generally not difficult to decode, but still required a specialist.

Cryptography became more widely used after Mary Queen of Scots, which meant that more and more people were learning the art of reading cipher text. Because of this, a more complicated form of cryptography needed to be created. Fortunately, Vigenere cipher was in the process of being perfected. Vingenere ciphers uses two or more alphabets instead of one, meaning each letter is equivalent to two (or more) cipher letters. This substitution cipher could be extremely confusing, which is why keywords were used to assist in discovering the alphabet. The addition of keywords made it so that only the people who had communicated with the author of the text had access to its cipher alphabets. 

 

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. 

Inviting Suspicion

We generally don't bother to encrypt messages if we have nothing to hide. By using a code or cipher, it's implied that the contents are sensitive or illicit in nature. In fact, as Singh points out, they're likely to be more explicit because the encryption lulls the sender into a false sense of security and they write more openly about their plans. So by putting too much faith in an easily breakable cipher, you risk incriminating yourself further.

In addition, by using a cipher or code that is easily identifiable as such, you automatically invite suspicion.  In her trial, Mary claimed she knew nothing about the plot, but even without decrypting the message, it was clear she was corresponding with conspirators. Also, the fact that she didn't write her message in plain text implies she was concealing something. In situations like these, it may be better to stick to some sort of code that masks the message as something innocuous, or some sort of steganography that hides the secret message within another. By finding a way to hide a message in plain sight, it helps divert suspicion in the first place rather than relying on an imperfect cipher once you've drawn attention.

The Consequences of Weak Encryption

One may assume that any type of encryption is better than no encryption, but for many situations, that may not be the case. Take the story of Mary Queen of Scots. Her weakly encrypted correspondence with Babington was interpreted by expert cryptanalysis Phelippes, leading to her eventual execution. Mary and Babington were so confident in their substitution cypher that they explicitly spoke about their plans to assassinate Queen Elizabeth. Unbeknownst to them, there had been huge advances in the field of cypher-breaking. Had Mary and Babington possessed an accurate sense in the weakness of their cypher, their conversation would have been far more discreet, taking care to discuss their plans in a more cautious manner.

This form of explicit versus discreet communication can be seen in everyday situations where cyphers are not involved. For example, if a group of bilingual people want to talk about someone nearby without their knowledge, the group will most likely switch to the second, less widely-spoken language. They would talk about said person without any filters, as they'd assume that no one around them would be able to understand what they are saying. However, if the group of people aren't lucky enough to have a second language to fall back on, they will probably communicate in a more discreet manner, with facial expressions and gestures, rather than clearly spoken words.

The case of Mary Queen of Scots could be a lesson to anyone who wishes to communicate through encryption- communicate as if your cypher is breakable, no matter how secure you might think it is.

 

The Value of Privacy

Why do you think that the advent of the telegraph motivated the use of a more secure cipher like the Vigenère cipher?

Prior to the telegraph, much of the communication was done so through hand written or typed correspondence. There was a sense of privacy when communicating through letters because they are sealed and it was assumed that only the intended recipient would read them. For people communicating more sensitive information, there was a chance that someone would intercept the letter and so enciphering it was standard in this case. The telegraph had the advantage of speed over the letter and so communication through telegraph was more favorable. However, a telegraph operator always reads the message when communicating via telegraph and so there is a decrease in privacy when using this system. This decrease in privacy could have been a motivation to use more secure ciphers like the Vigenère cipher. The only thing hindering people from using the Vigenère cipher over the Caesar cipher was the complexity and the amount of effort needed to implement the cipher. When there became a further decrease in privacy while using telegraphs, people may have realized that the extra effort needed to use the Vigenère cipher was worth it if it meant more privacy.

I think this can be seen presently with the advent of the Internet. The amount of privacy we have decreases when communicating through the Internet. To regain this privacy we do things like encrypt our data through the use of VPNs or by browsing websites that utilize SSL. A decrease in privacy because of the Internet has prompted us to go an extra step to regain it, and so it makes sense that the people that lived during the advent of the telegraph had done so as well.

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