### Unit 2: Basic Cryptographic Concepts

Encryption and decryption of data form the basis of information security. Cryptography is the science of encrypting data. In this unit, we will explore basic cryptography concepts and the purpose of cryptography. Also, we will look into the details of symmetric key encryption techniques. In particular, we will discuss the symmetric key algorithms called Data Encryption Standard (DES), Triple DES, and Advanced Encryption Standard (AES). DES is a block-cipher employing a 56-bit key that operates on 64-bit blocks. Triple-DES is a variant of DES that employs up to three 56-bit keys and makes three encryption/decryption passes over the block. In 1997, NIST initiated a very public, four-and-a-half-year process to develop a new secure cryptosystem for U.S. government applications. The result, the Advanced Encryption Standard, became the official successor to DES in December 2001.

**Completing this unit should take you approximately 7 hours.**

### 2.1: Basic Cryptography Concepts: Symmetric Encryption Algorithms

- Watch this video about the basics of information security and cryptographic concepts related to symmetric encryption algorithms like DES, Triple DES, and AES.

### 2.2: Purpose of Cryptography

Read section 2 about basic cryptographic concepts.

### 2.3: Data Encryption Standard (DES)

Read section 5.4 about DES symmetric key cryptography algorithm.

### 2.4: Triple DES

Read this page about how Triple DES makes use of DES to improve on encryption-based security.

### 2.5: Advanced Encryption Standard (AES)

Read section 5.9 about the advanced encryption standard (AES) algorithm.