Introduction

This book provides a detailed, hands-on guide to using the HEaaN library — when to use it, how to use it, and why it matters.

It is structured into a series of chapters, each focused on a specific aspect of homomorphic encryption with HEaaN. Starting from the basics — plaintexts, ciphertexts, and key management — the book gradually builds up to more advanced topics, including bootstrapping, which is one of the most powerful and defining features of FHE schemes.

Each chapter includes:

a brief introduction to the topic being covered,
a realistic scenario where the topic becomes relevant, and
a set of concrete tasks with example code that solves the problem.

Finally, the book walks you through the example code line by line, explaining how each HEaaN function operates within various encrypted computation workflow—from key generation to ciphertext evaluation and decryption. Whether you’re a new developer or looking to deepen your understanding of advanced homomorphic encryption features, this guide is designed to help you learn HEaaN step by step with clarity and purpose.

In this tutorial series, we introduce an imaginary company called SuperSecure, Inc. to create a more immersive experience. This company has adopted the HEaaN library to develop an FHE solution. You will take on the role of a new intern at SuperSecure, where each chapter assigns you specific tasks, and we demonstrate how HEaaN helps accomplish them. When you're ready, let's get started from Week 0 at SuperSecure, Inc.

Week 0 at SuperSecure, Inc.

👋 Welcome to SuperSecure, Inc. 🎉!

Welcome intern! We’re excited to have you on board!

SuperSecure specializes in secure computation services powered by CryptoLab's HEaaN library, which is based on the CKKS FHE scheme.

At the interview, you already learned what we are doing : we provide a range of solutions — from running computations on encrypted client data to enabling secure queries over encrypted databases. Whatever the use case, privacy always comes first.

You’ve just joined the team as an intern, and you're about to begin your journey toward becoming a homomorphic encryption expert. Your role will be to explore real-world scenarios and implement practical tasks using HEaaN.

At first, working with a homomorphic encryption library might feel a bit unfamiliar—but don’t worry! We'll walk you through HEaaN’s core APIs, with step-by-step explanations and hands-on exercises to help you get comfortable.

Ready to dive into the world of privacy-preserving computation? Let’s get started! 🚀

No portion of this book may be reproduced in any form without written permission from CryptoLab, Inc.

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The HEaaN Book

Introduction

Week 0 at SuperSecure, Inc.