This book provides an overview on various methodologies and procedures of cryptography. In the times of escalating worldwide development of electronic data storage and communications, efficient security of information has become a crucial need. The most efficient tool for the protection of information is cryptography, used in a combination with other tools for assuring the security of information in all of its applications, including user authentication, data integrity and confidentiality. This book is a compilation of in-depth research work in the field of cryptography. It describes some of the crucial challenges faced by the present computing world as well as a few techniques to defend against these challenges. It aims at serving as a useful source of reference for engineers, graduate and doctoral students, researchers, faculty members of universities, etc.