Information Security has become an important element of data communication. Various encryption algorithms have been proposed and implemented as a solution and play an important role in information security system. The two most basic facets of modern day data encryption are data privacy and authentication. As modern society becomes more connected, and more information becomes available there is a need for safeguards, which bring data integrity and data secrecy. Cryptography is the one of the main categories of computer security that converts information from its normal form into an unreadable form by using Encryption and Decryption Techniques. This book explains the fundamentals of confidentiality, authenticating, and cryptography. The significant aim is to show the remarkability of applying security in any information system implemented. The book also provides a study on the recent modern cryptography algorithms applied in security especially on embedded systems such as the mobiles.