A Cryptography Primer

Cryptography is a very vast field. So, we will learn only the basics of cryptography in this section.

Cryptography

One of the most central pieces in cryptography is the cipher.

Cipher

A cipher is an algorithm for converting a piece of data, called plaintext, into another piece of data, called ciphertext, which appears as random data and reveals no information about the original data.

We can also define a cipher as a pair of efficient algorithms $(E, D)$ where:

• $E$: $K \times M \to C$ is an encryption function receiving a plaintext (M) and a key (K) as an input and providing a ciphertext (C) as an output.
• $D$: $K \times C \to M$

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