Secret writing was apparently more advanced and the administrators are used secret codes to communicate with a network of spies spread out through the country. This book focuses on the authentication, confidentiality and the limitations existing in the present methods. Information security refers to protecting information and information systems from unauthorized access. The main objective of this book is to develop a more secured and authenticated system using a Modified Message Digest Algorithm (MMD). In this process a concept called cheating text is introduced for providing confidentiality...