Cyber security is the protection of information systems, hardware, software, and information as well from theft, damages, interruption or misdirection to any of these resources. In other words, cyber security focuses on protecting computers, networks, programs and data (in use, in rest, in motion) from unauthorized or unintended access, change or destruction. Therefore, strengthening the security and resilience of cyberspace has become a vital homeland security mission. Cyber security attacks are growing exponentially. Security specialists must occupy in the lab, concocting new schemes to preserve the resources and to control any new attacks. Therefore, there are various emerging algorithms and techniques viz. DES, AES, IDEA, WAKE, CAST5, Serpent Algorithm, Chaos-Based Cryptography McEliece, Niederreiter, NTRU, Goldreich–Goldwasser–Halevi, Identity Based Encryption, and Attribute Based Encryption. There are numerous applications of security algorithms like cyber security, web security, e-commerce, database security, smart card technology, mobile security, cloud security, digital signature, etc. The book offers comprehensive coverage of the most essential topics, including: Modular Arithmetic, Finite Fields Prime Number, DLP, Integer Factorization Problem Symmetric Cryptography Asymmetric Cryptography Post-Quantum Cryptography Identity Based Encryption Attribute Based Encryption Key Management Entity Authentication, Message Authentication Digital Signatures Hands-On "SageMath" This book serves as a textbook/reference book for UG, PG, PhD students, Teachers, Researchers and Engineers in the disciplines of Information Technology, Computer Science and Engineering, and Electronics and Communication Engineering.