Authors: Dr. P. Venkadesh, Dr. S.V. Divya, Dr. M. Padmapriya and Dr. Mercy Bai. G

ISBN: 978-81-69857-74-1

DOI: https://doi.org/10.59646/825

Date of Publication: September 28, 2026

Preface

Information security has become a fundamental component of modern computing because digital information is continuously generated, processed, stored, and exchanged across interconnected systems. The rapid expansion of cloud computing, mobile applications, Internet services, distributed systems, artificial intelligence, and networked devices has increased the importance of protecting information from unauthorized access, modification, disclosure, disruption, and destruction. A strong understanding of information security therefore requires knowledge of cryptographic algorithms, authentication mechanisms, key management, security protocols, and the mathematical principles that support modern security technologies. This book, Information Security, is designed to provide Computer Science and Engineering students with a systematic foundation in these essential concepts.

The book begins with the principles of Classical Encryption, introducing the basic concepts of security attacks, services, mechanisms, cipher characteristics, and security standards. Classical substitution and transposition techniques provide the conceptual foundation for understanding how plaintext can be transformed into ciphertext and how cryptographic systems attempt to resist attacks. The discussion then progresses to Symmetric And Stream Ciphers, covering block cipher principles, DES, finite field arithmetic, AES, block cipher modes of operation, random number generation, and stream ciphers. Particular emphasis is placed on the structural and operational principles of widely recognized symmetric cryptographic algorithms.

The third unit introduces Asymmetric Ciphers, where mathematical concepts such as modular arithmetic, prime numbers, Fermat’s and Euler’s theorem, and discrete logarithms are connected with public-key cryptography. Algorithms and protocols including RSA, Diffie-Hellman key exchange, and ElGamal demonstrate how asymmetric techniques solve important challenges associated with secure communication and key exchange. The fourth unit focuses on Hash Function and Digital Signature, explaining secure hashing, message authentication codes, HMAC, digital signatures, and the Digital Signature Standard. These mechanisms are essential for ensuring integrity, authenticity, and non-repudiation in digital communication.

The final unit addresses Key Management and User Authentication, covering key distribution, X.509 certificates, public key infrastructure, user authentication, and the Kerberos protocol. These topics connect cryptographic principles with practical security architectures used in enterprise and networked environments. Throughout the book, emphasis is placed on fundamental concepts, algorithmic principles, technical terminology, examples, and applications so that students can develop both conceptual understanding and practical awareness. The overall objective is to provide a strong foundation for further study and professional work in cybersecurity, cryptography, network security, secure software development, and information assurance.