The nbspmain aim of this paper is about how to protect information indigital form and to provide security services. However, a general overview of network security and cryptography is provided andvarious algorithms are discussed. The purpose of a digital signature is to provide a meansfor an entity to bind its identity to a piece of information. Thecommon attacks on digital signature were reviewed. The firstmethod was the RSA signature scheme, which remains today one of the most practical and versatile techniques available. Fiat-Shamir signature schemes, DSA and related signature schemes aretwo other methods reviewed.