This end-of-degree work consists of performing in a first stage, a historical journey of classical cryptography including the Enigma machina, indicating what it represented and its cryptanalysis. A second stage, consisting of the study of modern cryptography, including the current type of cryptography, its applications, and the reason for the most frequently used algorithms. Finally a third stage, where it will be practical, using cryptographic tools such as OpenSSL and Packet Tracer. These three stages will be developed by 7 tasks with the aim of analysing how reliable the algorithms most are used in modern cryptography.