Now in its second edition, this thoroughly revised text presents the principles, techniques, design and implementation of cryptography and information security algorithms. It offers a balance between the presentation of theoretical and practical aspects. To provide the mathematical background required to understand the principles of cryptography and information security, the text explains all the relevant theorems, such as Fermat's theorem and Euler's theorem. It provides a clear analysis of various encryption methods and cipher techniques. In addition, various security measures, such as firewalls, virtual private networks, and web security, are discussed. This edition also includes comprehensive coverage of new innovations and improvements in the field of cryptography and information security. Many solved numerical problems to clarify the various concepts and different algorithms are included, as are multiple choice questions with their answers. The book is intended for the undergraduate and postgraduate students of computer science and engineering, undergraduate and postgraduate students of computer science, information technology, and students of Master of Computer Applications.