Introduction to encryption

Encryption is the process of converting plain text into cipher text. The easiest way to explain why we need encryption is to imagine a scenario where we wish to transfer a file containing sensitive information (such as patient medical records) between two computers over an untrusted network such as the public internet, without being revealed by an untrusted third party.

Another example is a retail website, which processes the credit card information of its customers when they purchase products from the website.

To follow the Payment Card Industry Data Security Standard (PCI DSS), a standard for storing and processing credit card information, the retail company must encrypt all credit card information in transit and at rest.

Let's use a common three-tier architecture as an example – with front web servers (behind the load balancer for high availability), an application server (for processing the business logic), and a backend database...