Abstract:
It is impossible to imagine ourselves not involved in this tremendously increasingtechnology nowadays. In the field of networking, the area of network security consists of the provisions and policies adopted by the network administrator to prevent and monitor unauthorized access, misuse, modification, or denial of thecomputer network and resources that are network-accessible. Network security is acomplicated subject, historically only discussed by well-trained and experienced experts. However, as more and more we become "wired", all of us need tounderstand the basics of security in a networked world. In this research paper wetreat shortly the network concepts such as authentication and anti-virus softs and management of security which is different for all kinds of networks. So a small home or a workplace would only require basic security while large businesses will require high maintenance and advanced software and hardware to prevent malicious attacks from hacking and spamming. The term network security and information security are often used interchangeably. Information security uses cryptography to transform usable information into a form that renders it unusable by anyone other than an authorized user; this process is called encryption. Some history of cryptography is included, as well as an introduction that begins with Caesar Cipherand other used simple cryptosystems such as Shift, Substitution, Affine, Vigenere,Hill, Permutation, and Autokey Ciphers and the classification of modern cryptographic algorithms. In next session will be discussed S-Boxes as the most important part of SPN (Substitution-Permutation Network) that is a mixed transformation of bits in a number of rounds. What is more important is the non linearity of the s-box within a cryptosystem. That means that the function between the input bits and output bits must be non-linear. This gives the strengthness of analgorithm against attacks. The question is; how can this be achieved? There are several criterias that an s-box must satisfy to be non-linear. These will be described in an example then we go on with a software that examines the properties of the sbox.As a result will be defined if the s-box is appropriate to be used or not. What usreally matters is that what must be secret has to be a secret!
