Table of Contents This is part of a tutorial series on the CKKS homomorphic encryption scheme. In the last article, we covered some groundwork about polynomials and the CKKS encoding method. This article covers the encryption and decryption routines. Notably, if you already know about CKKS, we will deviate from a usual treatment for explanatory purposes. In particular, we will first define CKKS encryption, decryption, and basic operations without using the residue number system (RNS).