It tells us how to protect our data from unauthorized access, and what methods we can use to ensure that only authorized users have access to it. The book begins by explaining the importance of cryptography in today's digital world, where sensitive information is constantly being transmitted and stored electronically. The author emphasizes that cryptography is not just about encrypting data, but also about ensuring its integrity and authenticity. He discusses various encryption techniques, such as symmetric and asymmetric encryption, and their applications in different fields like e-commerce, online banking, and digital signatures. The book then delves into the details of public key infrastructure (PKI), which is a system for secure communication over the internet. PKI uses a pair of keys - one public and one private - to encrypt and decrypt data. The author explains how PKI works, including the process of certificate management and the role of certification authorities. Next, the book covers the topic of digital signatures, which are used to authenticate the sender of a message and ensure that the contents of the message have not been tampered with. The author discusses the different types of digital signatures, such as RSA and elliptic curve cryptography, and their applications in legal documents and other areas. The book also explores the concept of secure sockets layer (SSL) / transport layer security (TLS) protocols, which provide secure communication over the internet.

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