An interesting fact about the word cryptography is that it has Greek origins from the words kryptos and graphein, which translate to hidden and writing, respectively. Like I mentioned in my introduction, Cryptography has been around since the Ancient Egyptians. In , the Egyptians were some of the first peoples to put their mark on the beginnings of Cryptography (along with the Romans and Greeks). Cryptography started in the eastern hemisphere at a time where the Egyptians, Greeks and Romans wanted to not only keep their information as records, but to keep them secret and hidden from anybody else (Damico, 2009).
In the very beginnings of Cryptography, the methods of encrypting messages were not nearly as difficult or complex as they are now. The Egyptians used multiple forms of hieroglyphics to keep their writing hidden and misunderstood from other people who were not accustomed to the hieroglyphic language. The Egyptians would (many times) change the meaning of the hieroglyphs so as to keep any other people from understanding what is being written if it so happened that these people somehow received possession of the Egyptians writings.
The Greeks had a different method of encrypting messages at the time of their beginnings with Cryptography. At around 400 B.C., the Greeks invented a fancy tool called the Scytale. Below is a picture of the device. This tool was constructed with a long piece of leather with letters that had been imprinted on it. With this piece of leather, the Greeks would take the leather strip and wrap it around a stick with a particular diameter that is set. Doing so would unveil the message that is contained on the leather strip. However, one must have a cylinder with the same diameter in order to read the message on the leather strip. Otherwise, it would just be gibberish!
The Romans had a different take on Cryptography and came up with the famous shift cipher or, what is better known as the Caesar Shift Cipher. This cipher was rather effective in its time because the letters of the plain alphabet would be shifted a certain number of shifts which will then translate the plain text into the cipher text. Rumor has it that Caesar and the Romans typically preferred a shift of 3. The only problem with this particular cipher is that anyone could crack it if they tested out all of the possible shifts and eventually landed on the right shift that would decrypt a Roman message.
With the many early forms of cryptography, keeping messages a secret was a piece of cake until the practice of cryptography became more and more widespread. Because of this mass excitement with cryptography, more and more ciphers were more likely to be broken. Because of idea of secrecy is so crucial for civilizations, more advanced ciphers came to light in order to keep cryptography as a common practice.
One of the new methods of cryptography that came about was the Polyalphabetic Cipher. These ciphers use a mixture of multiple mix alphabets. This cipher was created and developed by Leon Battista Alberti in 1467. He created a polyalphabetic cipher that used the methods of mixing multiple alphabets (Rodriguez-Clark, 2013). Leons cipher shifted a mixed alphabet by a set number and used an uppercase letter to denote the instant when the mixed alphabet was switching. As an example, he would use one mixed alphabet for 5 letters and then switch to another mixed alphabet. It worked well in keeping secrecy within messages, but the cipher could easily be broken with an analysis called Frequency Analysis for each group of the mixed alphabet.
Another man came in later on down the road during the 15th century to create another type of polyalphabetic cipher. This man was Johannes Trithemius (Rodriguez-Clark, 2013). His particular cipher did not incorporate the idea of using a set number for switching the mixed alphabets. Instead, it used a table (like the one pictured below) to switch the mixed alphabets after each letter. The only problem with this cipher is that it lacks a key for decryption. Because of this, if someone understood how the cipher worked, they would be able to crack any code that was created through this cipher. They were all created in the same way and, therefore, could all be broken the exact same way. This was crucial to the development of cryptography because it led to much greater things (Rodriguez-Clark, 2013)!
After the attempt of Trithemius, another polyalphabetic cipher was created that was quite similar to his. The difference with this one was that it used a key and happened to be much more difficult to crack. In fact, it was thought of to be an unbreakable cipher! A man by the name of Giovan Battista Bellaso in 1553 created this new cipher; however, this cipher is actually credited to Blaise de Vigenere because he created a similar cipher in the 19th century (Rodriguez-Clark, 2013). This cipher used a table similar to the cipher of Trithemius, but instead of starting by looking at the A in the first column and the first plain text letter in the row, resulting in their intersection being the new coded letter, the key would take up the columns and then the plain text would be down the rows so that the intersection of the first key letter and the first plain letter resulted in the coded letter. This was really difficult to break and still is now because of the use of a key. Without the key, one must then analyze the coded text to see if there exist any noticeable patterns. This cipher is considered one of the biggest step for over 1000 years in the development of cryptography. The idea of the inner-workings of this cipher would be an idea that many future cipher would adopt.
One such cipher, which also happens to be the most famous, was the Enigma machine that was used during World War II. The German army used this machine as the new and improved form of cryptography that used Vigeneres idea of a polyalphabetic substitution cipher. This machine consisted of a group of disks that rotated, along with plugs that switched certain letters under certain settings. Many thought this form of cryptography was impossible to break. Below is a video that explains the inside of an Enigma machine:
Breaking this Enigma machine cipher was critical to the outcome of WWII (in fact, it has been said to have stopped the war almost 2 years earlier than if it would not have been cracked). It is astounding the vitality of the role that cryptography has played throughout its existence. It has reared its head quite a bit during times of war, where keeping messages secret as they are transported across the world.
Cryptography is still around and widely used today! I will continue on later about its significance and application later on, but first , let us move on to the mathematics behind it all!