Razvoj sustava za kriptiranje

Jakovljević, Filip. (2011). Razvoj sustava za kriptiranje. BSc thesis. Filozofski fakultet u Zagrebu, Department of Information Science. [mentor Stančić, Hrvoje].

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Abstract

Cryptology (or cryptography) is a science which deals with the encryption of messages. There are a lot of ways to encrypt a message, that is, a lot of different systems that can be used, and the development of cryptology as a science can be easily traced if we examine the development of these systems that were used. Chronologically, the development of encryption systems can be divided into several longer periods of time: classical cryptology, medieval cryptology, cryptology from 1800. to World War Two, the World War Two cryptology, and finally modern cryptology. In its beginnings, cryptology was very simple and was used mostly for fun, because of its misteriousness, until it acquired a more serious purpose – in the military. When it comes to the first more advanced encryption systems, one should mention the Atbash cipher, the Polybius Square, the Caesars cipher and the Scytale. All of these systems were basically simple, but at the same time very effective, since the enemy was unfamiliar with the way they worked. In the Middle Ages, the systems started to incorporate mathematics, which would soon become the leading science in the field of cryptology, despite the fact that the subjects of encryption were exclusively letters. At that time what was also invented was tabula recta, soon the critical component of the Vigenére cipher, which would later be used as a part of much more developed systems, some of which are used even today. Such a sudden development of these systems was a result of the invention of the cryptoanalytic frequency method, which made every monoalphabetic systems easily cracked. Cryptology continued to develop rapidly, especially during the two world wars. During World War One, it played an important part and many polyalphabetic systems such as the Playfair cipher, the Hill cipher and the Jefferson wheel were used, but World War Two was when the revolution of cryptology occurred, thanks to Arthur Scherbius. This German engineer invented a machine for encryption which used mechanical and electronic subsystems. Due to a very complex and advanced way of functioning, as well as many different versions of the machine used, primarily, in the German army, it took a long time to crack that system, but eventually resulted in ending the war. With the invention of computers, cryptology succeeded in making one more leap forward and entered the everyday life, resulting in the introduction of the standard algorythm for encrypting (Data Encryption Standard) and its more advanced successor AES, as well as the creation of public key sytems, most well-known of which is the RSA system.

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