Cryptography

The History and Mathematics of Codes and Code Breaking

Tag: Vigenere Cipher

Necessity is the Mother of Invention

The invention of the telegraph revolutionized long-distance communication by allowing messages to travel many miles practically instantaneously. However, the drawback of telegraphs compared to letters was that the required intermediaries for transmission also had access to the contents of a message. While a postman is unlikely to open and read a sealed letter, a telegraph clerk has no choice but to read what they are sending.

This affected the development of cryptographic techniques in two major ways. One, it prompted the general public to become more interested in cryptography. Even if their messages were not necessarily "secret" per se, most people are uncomfortable with the idea of a half-dozen people reading their private correspondences. Two, individuals and organizations that already encrypted their messages needed to amp up their security, because their messages would be viewed by more people and their messages would be easier to intercept via wire tapping. This spurred the adoption of the Vigenère cipher for telegraph communications because of the increased security it provided.

Similarly, in recent times, the concept of encryption has become more popular and the technique has become more refined in response to the increase in digital communications. As new technologies emerge, so may new cryptographic techniques.

Prying Telephone Operators and Free Radio Waves: Implications of New Tech on Secure Messages

Because the onset of the telegraph inserted a middleman in the communication of a sender and receiver, messages not meant for prying eyes understandably needed to be encrypted with a more secure cipher like the Vigenère cipher. Since the invention of the telegraph in the 19thcentury, several other inventions or innovations in the world of communication have simultaneously increased the global spread of information, while also creating significant implications for security and privacy.  For example, with the first primitive forms of the telephone, an operator was needed to connect the caller to their recipient. This operator could hypothetically listen to any call they wanted to, which created a feeling of insecurity in this form of communication that was quite similar to that of the telegram—that of distrust in a middleman (or woman, as switchboard operators at this time were often female). Similarly, with the invention of radio in the 20thcentury, any message sent over radio waves could be picked up freely, so messages necessarily needed to be encrypted if they contained sensitive material, especially in times of war, as information gathering agencies would often employ this tactic to collect knowledge on the plans or whereabouts of their enemies. Needless to say, every technological advancement brings with it uncertainty, and the risk of cession of privacy or security should be considered before any advancement in communication becomes widespread.

Breaking (Almost) Unbreakable Ciphers

The strength of the Vigenère Cipher depends largely on the length of the keyword. If the keyword is just one letter, then it is nothing more than a simple shift cipher; if the keyword is the same length as the plain text, there will be little to no discernable pattern. However, Singh clearly demonstrates that even with a keyword as long as the text, breaking the Vigenère is doable by guessing common words like "the."

Even though it is relatively straightforward to break even these more secure ciphers, doing so in practice is often much harder. Primarily, this is because of the amount of guessing and checking required and the creative insights necessary to realize the best way to break the code. During the process of deciphering the message, and essential step is guessing words either in the plain text or in the keyword, and if your guess is wrong, you have to backtrack until you are confident that all of your work is correct and start from there again. This makes the process of cryptanalysis tedious and time-consuming.

Once you know what method to use to break the cipher, deciphering the message is only a matter of time, but often, figuring out how to approach a complicated cipher takes even the smartest cryptanalysts years to figure out on their own. For example, breaking the simple Vigenère cipher was not difficult; once Charles Babbage figured out how to break it, the Vigenère went from being an unbreakable cipher to extremely insecure overnight. This demonstrates that breaking the cipher itself is often not the most difficult part; the hardest part of breaking complex ciphers is coming up with a foolproof method which exploits weaknesses in the cipher.

Technologies Effect on Cryptography

The advent of the telegraph was a major factor in the use of the Vigenère Cipher. Due to the Vigenère Cipher having 60 cipher alphabets, the methods of encrypted methods not only increased but became ideal for technology such as the telegraph.  What makes the telegraph go well with the Vigenère cipher is that it brought more security to the encoded message. It did this by eliminating the people who are knowledgeable about the message. An example of this is two people wanting to send a message to eachother via morse code. To do this they would have to have two middle men who were trained to use the telegraph send the message. Without the Vigenère cipher, those two middle men would be aware of the message thus exposing the information. Cellphones have changed the way we communicate greatly, especially in terms of making a transaction or giving away credit cart information. Personally, though I know it might be safer but is still at risk, when I exchange credit card information with my family, I do it over the phone rather than text. Cellphones have a major effect on secrecy in society today. Many people have codes on their phones and every ones' phone is encoded in some type of way. Implications arise when or if someone is able to break the basic encryption for a chain device such as the iPhone. If this happened then everyone with an iPhone will be at risk of a security breach.

The Smithy Code: A Look Into Multiple Encryption

On Elonka's website, there is an explanation and solution to the Smithy Code. The Smithy Code was embedded in the ruling for a plagiarism trial concerning Dan Brown's The Da Vinci Code. Justice Peter Smith italicized several letters which spelled out "S m i t h y c o d e J a e i e x t o s t g p s a c g r e a m q w f k a d p m q z v -" -- "Smithy code" is in English, and the rest is ciphertext which evidently involves a polyalphabetic substitution cipher. According to the explanation, Smith used a series of Caesar shifts based on the letters that correspond to the numbers of the Fibonacci sequence. Usually, this would be 1-1-2-3-..., which would correspond to A-A-B-C-.... However, Smith added a twist and replaced the letter B with the letter Y. He then used a grid of the Caesar shifts and found the plaintext letter in the grid, then traced it up to the letter at the top of the column to encipher it, similar to the way one would decode a Vigenère cipher.

In class, we have discussed Caesar ciphers, polyalphabetic substitution ciphers, and the Vigenère cipher (a type of polyalphabetic cipher). The Smithy Code was an intricate interweaving of all of these methods and a method inspired by The Da Vinci Code (the Fibonacci Sequence), because of the novel's relevance to the trial. It was a fascinating look into a method by which several ciphers can be used, and how far common knowledge and research about cryptography has come in order for these methods to be implemented.

4 Codes, 1 Sculpture: Kryptos

During the talk Elonka gave to the class on Friday, I found myself fixating on one thing, Kryptos. I was so surprised by the fact that there was a statue located on the grounds of the CIA, which has an unsolved code written on it. The CIA are supposed to be some of the greatest minds of our time, and they can't solve a cipher that is quite literally sitting right in front of them.

To give a little more information, Kryptos is a large sculpture which contains four codes. Each of these codes was placed onto the sculpture by stamping through the metal, so that the letters are holes in the metal. The four codes were created by Ed Scheidt, who at the time was the Chairman of the CIA Cryptographic Center.  The first three codes have been solved, by the public and from within the CIA, but the fourth remains a mystery.

The connection between Kryptos and our course is fairly obvious. Four encrypted messages, or codes, in a class about codemaking and codebreaking? Sounds like exactly what we're looking for I think. It's also worth mentioning that the first codes use a Vigenere cipher, something that we were discussing in class at the time Elonka came to visit. Vigenere ciphers were the code standard for quite some time, so it doesn't surprise me at all that they were used for a sculpture as famous as Krpytos.

Many famously unsolved codes were solved at a much later time. With this famous code sitting in front of some of the world's best codebreakers, I am sure that Kryptos will soon be cracked. Maybe Elonka will be the one to solve Kryptos, or maybe even one of the students of our course.

Here's a link to her Kryptos page: http://elonka.com/kryptos/

Environments that promote or discourage confidence in codes

Before the development of the Vigenère cipher, those sending encrypted messages understood that if the message was found, any good codebreaker would be able to decipher it. Mary Queen of Scots experienced a very different environment. She had total faith in her cipher and never guessed that anyone would be able to decipher her messages if they were intercepted. Because of this, Mary Queen of Scots did not bother to write discretely about her plans with her aides.
Before the Vigenère cipher was developed, those that wrote and sent encrypted knew the risk of interception did not speak so plainly about the topic of the message as someone that had confidence in their encryption would. This kind of environment that fostered insecurity was complete with numerous Black Chambers. Black Chambers were centers where messages intercepted through the mail system were then analyzed and attempted to be deciphered. Through this, valuable messages that had been deciphered could be then given or sold to various European powers as crucial intelligence.
Due to these kinds of operations, there was no way for people to be totally confident in their ciphers, something that got Mary Queen of Scots executed. The development of Vigenère cipher allowed for a greater confidence in the security of people's messages.

Persistence is the "key"

New things can seem very challenging at first. For example, a question seems so much simpler when we already have an answer to it. However, the question without the answer can seem very daunting, making it seem too difficult to even attempt. This is very similar to how the pattern of ciphering worked. First there was the shift cipher. When people realized what it was, it was extremely simple to decipher. Then there was the substitution cipher. This took a while for people to decipher. Some gave up, but then the Arabs developed frequency analysis. Once people understood frequency analysis, it was relatively easy to break.

Then came the Vigenere cipher. People were baffled. They didn’t understand how to break it, so many gave up in the process. They understood the concept but did not understand how to cryptanalyze it. Because people did not have a known way of breaking into the cipher, they simply gave up. However, it took cunning and persistence from Babbage to finally crack it. Once the way to crack it became relatively well known, people could easily decipher Vigenere ciphers with a little bit of time.

The reason why people gave up so easily is not because they did not want to break it but because they did not know where to start. With a new cipher, the cryptographers have the advantage over the cryptanalysts. The cryptanalysts were so used to frequency analysis that when a new “unbreakable” cipher came out, they did not know how or where to tackle it from. This led to lots of confusion and most of them simply giving up rather than persistently experimenting with different techniques.

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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