Encryption is basically the process of modifying data or information to make it unreadable or unusable without a secret key, which is only given to people who are expected to read the message. The difference between encoding or packing and encryption is that packing doesn't use any key, and its main goal is not related to protecting the information or limiting access to it compared to encryption.
There are two basic techniques for encrypting information: symmetric encryption (also called secret key encryption) and asymmetric encryption (also called public key encryption):
- Symmetric algorithms: These types of algorithms use the same key for encryption and decryption. It's a secret key that's shared by both sides:

Figure 21: Symmetric algorithm explained
- Asymmetric algorithms: In this algorithm, two keys are used. One is used for encryption and the other is used for decryption. These two keys are called the public key and the private key...