This element consists of three connected cogwheels, each of them with a letter. The middle cogwheel is mobile, with a mechanism allowing it to be pulled out, have its position changed and returned into the system.
This element can be used for researching transfer of energy from one cogwheel to another, but it is also a model of enigma. Have you ever heard of enigma?
Cryptography is a branch of mathematics which studies methods for sending messages in such a form that only those that they were intended for can read them. Terms coding and encryption are often confused. The aim of encryption is to hide the message, while the purpose of coding the message is to enable detection and correction of mistakes that appear during the transfer of the message via a communication channel. Messages are enciphered and deciphered with the help of a key.
Enigma is a cryptographic device used for enciphering and deciphering which uses a Vigenère cipher (type of substitutional cipher). The great Roman emperor Caesar also hid messages, using an encryption process that we call Caesar’s cipher (the Viegner’s cipher is its generalization). Using this messaging element, we can encipher and decipher using the Caeser’s cipher as well.
The first version of the enigma was invented in 1918. The original enigma and its improved version were used by the Germans between the two world wars and in World War II. During World War II, a team led by the great mathematician Alan Turing “cracked” the enigma, which enabled the Allies to read the secret communications of the opposing side. To solve the enigma, Alan Turing developed a computer that paved the way for the development of today’s modern computers.
On this element, you can learn about the transfer of energy from one cogwheel to another. However, you can do much more. You can use it to hide messages! How? In order to encipher and decipher, you need a key. The key for the enigma is a three-letter word. We will use an example to explain how to lock the enigma. Imagine that the word LAV (Croatian word for “lion”) is the key. Set the first cogwheel on the left so that the first arrow shows the letter L. After that, set the second cogwheel so that the second arrow shows the letter A, making sure you don’t move the first cogwheel. Finally, you set the last cogwheel so that the last arrow shows the letter V, making sure you don’t move the first two cogwheels. After you have locked the enigma, you can move on to enciphering and deciphering. We encipher by setting the letter of our choice to the last, 3rd arrow, and we read the encrypted text alternately from the 1st and 2nd arrow. How do we decipher? We set the letters of the encrypted text alternately on the 1st and the 2nd arrow, while reading the original from the last arrow. Notice that the processes of enciphering and deciphering are mutually inversed, which allows for successful communication, but only for those who lock the enigma with the same key.
Caesar was the general in ancient Rome who fought a lot of wars, so he needed to come up with a new method of hiding messages. How did he do it? By replacing each letter of the alphabet with the letter three places after it in the alphabetical order. Number 3 is the deciphering key that Caesar used. When we know the key of Caeser’s code, it is easy to decipher the message by replacing every letter of the alphabet with the letter that is found three places after it in the alphabetical order. Notice that the key can be any number k from the set {1,…,25} and all such ciphers used today are called Caesar’s ciphers.
- Turn one cogwheel clockwise. Do the rest of the cogwheels turn as well? In what direction? Faster or slower? What do you think would happen if cogwheels weren’t identical?
- Think of a three-letter word. Try to set the cogwheels so that the arrows show the word you have in mind. Can you always do that without taking out the middle cogwheel? Why?
- Find the cogwheel which has letters of the English alphabet listed in alphabetical order. How can it help you to decipher using the Caesar Cipher? Do you know which letter Caesar used to encipher the letter Z? Use this element to decipher the message hidden with the Caesar cipher by using the key which Caesar used: ulmhnd.
- Using CTK key, using the enigma, encipher the following message: Enigma is really cool!
- How many different keys can you set for the enigma?
