Analisis Sandi Algoritma Enkripsi Substitusi permutasi 4 Ronde

Encryption is one of the most important components in security of application of information technology. We need the good knowledge of encryption attack, to create the strong, rapid, and flexible encryption algorithm. This research shows that security of encryption algorithm does not only depend on the bits number of key, but also depend on the structure of algorithm itself. The more complicated the algorithm is (it is hoped more secure) the slower the algorithm runs, so the algorithm is not comfortable to be used. This research includes cryptanalysis and programming to attack the algorithm of simple encryption, 80-bit key, which can be broken theoretically in 19 years using 1 million computers, with brute force attack. In this research, this algorithm can be broken less than one minute with 10 thousand characters of known plain text with one personal computer, although the algorithm has good statistical property. Keywords: encryption, cryptanalysis, brute force attack, statistical property, known plain text