Encrypted communication is nothing else but a special form of communication. At the beginning there must be someone who wants to pass on some information, and at the end there is someone to receive it.
However, sometimes we don't want anyone else to know the information. And then we can use a cipher to hide it. If the recipient knows the way we encrypted the message, only he will be able to learn it.
When mentioning secret codes, most people immediately think about Enigma encryption machine. The Enigma became not only a symbol of complex ciphers, but also of the Allies' victory over Nazi Germany in World War II.
The original Enigma was a commercially patented machine. It contained a classic keyboard and two rotors, which rotated after entering the letter, making it impossible to break by force.
The one who wanted to read the message had to have his machine set up in the same way as the one who sent it, otherwise he simply did not get to the content.
German military machines used an even larger number of rotors, so the situation for deciphering the code further complicated. However, even before the war, Poland managed to find out the principle according to which the coding was based and some important information, which later served to definitively break the Enigma.
This happened in the UK thanks to a team led by the genius mathematician Alan Turing.
Tricks with Alphabet
However, encryption was used long before the existence of mechanical engines. Well-known is for example the so-called Caesar cipher, which uses the exchange of a letter for a letter standing in the alphabet by a precisely defined number of places further (typically if we decide that the shift will be two places, we write A as C and B as D, etc.).
This cryptographic pattern was useful at a time of low literacy, but later became too easy to break.
A significant advance in the coding of secret messages occurred with the discovery of the Vigenère cipher - it is similar to the Ceasar cipher, but uses several alphabets instead of one.
The so-called Vigenère square actually contains 26 of them. A message is then encoded and decoded with a code word that must be known by both parties; its accidental breakthrough is thus very difficult.
Gradually, other possibilities of encryption emerged, for example, with the expansion of books, it was possible to code a message using a specific book, which is a cipher that is essentially unbreakable by force, but very prone to revealing the key, i.e. the book itself.
Ciphers in Pop Culture
In modern times, books and film have succeeded in raising awareness of ciphers among the general public. Readers of Dan Brown's books have been traveling with protagonist Robert Langdon around the world for many years, searching for ancient secrets encrypted in symbols on famous buildings and works of art.
A similar topic was introduced in the literature by Umberto Eco, for example in his book Foucault's Pendulum.
In the movies, we sometimes come across coded messages from manic killers who like to play with the police and only if investigators crack their mysterious notes, they can prevent more murders from happening. A popular topic is also the aforementioned breakdown of the Enigma code.