1.2. Common Cryptographic Primitives

As claimed at the outset of this chapter, it is rather difficult to give a precise definition of the term cryptography. The best way to understand it is by examples. In this section, we briefly describe the common problems that cryptography deals with.

1.2.1. The Classical Problem: Secure Transmission of Messages

To start with, we introduce the legendary figures of cryptography: Alice, Bob and Carol. Alice wants to send a message to Bob over a public communication channel like the Internet and wants to ensure that nobody other than Bob can make out the meaning of the message. A third party like Carol, who has access to the communication channel, can intercept the message. But the message should be wrapped ...

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