Exploring the World of Fully Homomorphic Encryption (FHE) and Concrete ML: A Step Towards Privacy-Preserving Machine Learning
Mar 13, 2024
7 min Read

Introduction
In today’s data-driven world, where organizations collect and analyze vast amounts of sensitive information, ensuring data privacy and security is paramount. This blog post by Cluster Protocol dives into two innovative technologies, Fully Homomorphic Encryption (FHE) and Concrete ML, that offer a promising solution: enabling advanced data analytics and machine learning (ML) tasks while preserving privacy.

What is Fully Homomorphic Encryption (FHE)?
FHE is a revolutionary cryptographic technique that allows computations to be performed on encrypted data without decryption. Imagine being able to perform complex calculations on confidential information without ever revealing its contents! This groundbreaking capability opens doors for secure collaboration and analysis across various parties, fostering trust and protecting sensitive data.
Imagine you have a secret message or number (let’s call this ‘m’). You want to keep this secret safe, so you put it in a special kind of safe that only you can open (this is the “Encrypt” step, which turns ‘m’ into ‘Enc(m)’).
Now, the cool thing about this safe is that even though it’s locked, you can still perform some magic on it. Let’s say you want to do a math operation on your secret number, like adding 2 or doubling it, without actually taking it out of the safe. Normally, you’d have to unlock the safe, do the math, and then put the result back in and lock it up again.
But with this special Fully Homomorphic Encryption safe, you can do the math directly on the locked safe (the ‘f’ function on ‘Enc(m)’), and it changes the secret inside accordingly, without ever opening it! The result is a new safe that, when eventually opened (‘Decrypt’), reveals the result of your math operation directly on your secret number (the ‘f(m)’).
Ideal Use Cases
Homomorphic encryption is ideal for some use cases more than others.
Cloud / Distributed Computing
FHE enables secure computations on encrypted data stored in the cloud without the need to decrypt it. This preserves the confidentiality of sensitive data even when processed by third-party cloud service providers.
Data Analysis and Actions
FHE allows for analysis and performing actions on encrypted data without revealing the actual content analysts. For instance, healthcare providers can conduct statistical analysis on confidential patient information without decrypting it, thus maintaining patient privacy.
Machine Learning
FHE enables machine learning models to be trained on encrypted data. This is beneficial when data owners are hesitant to share their data for privacy reasons. With FHE, data remains encrypted during the model training process, and only the encrypted model is shared.
Accounting / Banking
FHE allows financial institutions to analyse encrypted financial transactions for fraud detection while maintaining client confidentiality.
Blind and Private Databases
FHE allows encrypted search and querying of databases without exposing search criteria or database contents, thus ensuring privacy for data owners who want to allow others to search and access information.
Threat Model
Homomorphic encryption is not a silver bullet for all use cases. As with all cryptography, how practical or safe it is to use is ultimately dependent on the use case, implementation, library, and underlying scheme.
Key Points:
* End-to-End Privacy: Data remains encrypted throughout processing, safeguarding privacy from start to finish.
* Revolutionising Data Analytics and ML: FHE paves the way for secure collaboration and analysis, enabling valuable insights without compromising confidentiality.
FHE Resources and Support
* Fully Homomorphic Encryption Consortium (FHE): This leading platform provides valuable resources, tools, and support for anyone interested in exploring FHE technology. Their website offers documentation, tutorials, and community forums, making it a one-stop shop for learning and development.
* International Association for Cryptologic Research (IACR): IACR hosts regular conferences and workshops dedicated to cryptography, including those focusing specifically on FHE. These events offer opportunities to learn from leading researchers, network with colleagues, and stay up-to-date on the latest advancements.
* Open-source FHE libraries: Several open-source libraries implement various FHE schemes, allowing developers to experiment and build applications. Popular options include HElib, SEAL, and PALISADE. These libraries often come with documentation, tutorials, and active communities for support.
* Academic publications: Numerous research papers and articles explore different aspects of FHE. While some might be more theoretical, others delve into practical applications and implementation details. Consulting academic publications can provide in-depth knowledge and insights for advanced users.
* Industry forums and communities: Online communities dedicated to cryptography and FHE offer valuable spaces for discussion, troubleshooting, and collaboration. Platforms like Reddit, Stack Exchange, and specialised FHE forums can be valuable resources for practitioners and enthusiasts.
* FHE startups and companies: Several companies are actively developing FHE-based solutions and tools. Engaging with these companies can provide insights into practical applications and potential career opportunities in the field. Remember, it’s crucial to research their offerings and reputation before engaging.
Select an FHE library
* FHE libraries: These are software libraries providing tools and functionalities to work with FHE.
* FHE Scheme: This refers to the specific mathematical framework and construction used to achieve FHE in a library. Different schemes offer varying levels of efficiency, security properties, and capabilities.
Therefore, selecting an FHE library “by scheme” involves choosing a library that implements the desired FHE scheme best suited for your specific needs and application. The table in the previous response provides a breakdown of popular FHE libraries categorized by the schemes they support.
For example, if you require an FHE library for performing computations on real numbers with approximate results, you might choose a library that implements the CKKS scheme like HEAAN or PALISADE. Conversely, if you prioritize good performance and user-friendliness for basic homomorphic operations, libraries like SEAL implementing the BFV scheme could be a suitable option.
By Language
Selecting the most suitable FHE library depends on several factors, including your preferred programming language, your specific needs, and your experience level. Here are some popular FHE libraries categorized by language:
C++:
* HElib: Offers a versatile implementation of the BGV scheme with bootstrapping and the CKKS scheme for approximate number computations.
* SEAL (Microsoft): Popular library known for its good documentation and user-friendliness. Implements the BFV and CKKS schemes.
* PALISADE (OpenFHE): Open-source library offering various FHE schemes with high performance and customization options.
Python:
* HEAAN-Python: Python binding for the HEAAN library, supporting fixed-point approximate arithmetic.
Go:
* lattigo: Provides various lattice-based cryptography implementations, including FHE schemes.
Rust:
* [fhe.rs](http://fhe.rs): An experimental library implementing the BFV scheme, offering good performance compared to other languages. While still under development, it shows promise for future advancements.
C:
* libScarab: Implements an FHE scheme using large integers.

By Scheme
BFV (Brakerski/Fan-Vercauteren):
Designed for efficiency and ease of use, offering good performance for basic homomorphic operations on integers.
Well-suited for applications requiring fast and secure computations on binary data.
* HElib: Offers a BGV implementation with bootstrapping, but not the primary focus.
* SEAL: Implements the BFV scheme with good performance and user-friendliness.
* PALISADE (OpenFHE): Offers a BFV implementation alongside other schemes, allowing for flexibility.
* FV-NFLlib: A header-only library focused specifically on the BFV scheme.
BGV (Brakerski-Gentry-Vaikuntanathan):
More versatile than BFV, allowing for bootstrapping and computations on larger integers.
Offers advanced features like multi-party computation, but might have lower efficiency compared to BFV for basic operations.
* HElib: Primarily focuses on the BGV scheme with bootstrapping and advanced features.
* PALISADE (OpenFHE): Provides a BGV implementation alongside other schemes.
CKKS (Cheon-Kim-Kim-Song):
Enables homomorphic computations on real numbers with controlled approximation errors.
Ideal for applications requiring computations on continuous data like scientific simulations or financial modeling.
* HElib: Offers an approximate number CKKS scheme for computations on real numbers.
* HEAAN: Provides a production-ready CKKS implementation with native support for fixed-point approximate arithmetic.
* PALISADE (OpenFHE): Includes a CKKS implementation with various features.
TFHE (Fully Homomorphic Encryption over the Torus):
Supports computations over a specific range of real numbers while offering good efficiency.
Less common compared to other schemes, but can be useful for specific applications requiring homomorphic computations within a bounded range.
* SEAL: Does not currently support TFHE.
* PALISADE (OpenFHE): Does not currently support TFHE.
* HElib: Does not currently support TFHE.
* [fhe.rs](http://fhe.rs) (experimental): Offers an experimental implementation of TFHE with potential for future advancements.
* Concrete-Rust (Zama): Implements the TFHE scheme, targeting the Rust language and offering good performance.
* Jaxite: A TFHE implementation in JAX, targeting Tensor Processing Units (TPUs) for accelerated computations.

Concrete ML: Putting FHE into Action
Concrete ML, developed by [Zama](https://www.zama.ai/), takes FHE a step further by offering a privacy-preserving ML framework. This framework leverages FHE’s power to perform ML tasks on encrypted data. Organizations can now train models and extract valuable insights from their data while maintaining complete privacy.
Benefits of Concrete ML
* Secure and Privacy-Preserving Data Analysis: Organizations can unlock the power of data analysis across various industries (healthcare, finance, telecommunications) without compromising individual privacy.
* Ease of Use: Data scientists can leverage familiar APIs, akin to those in scikit-learn. No need to be a cryptographer — Concrete ML abstracts the complexity.
* Built-in Models: Ready-to-use FHE-friendly models, resembling scikit-learn and XGBoost counterparts.
* Custom Models: Develop your quantization-aware models using PyTorch or keras/tensorflow and import them into Concrete ML via ONNX.
Concrete ML in Action
Unlock a world of possibilities with Concrete ML:
1. Healthcare Data Analysis: Improve patient care by securely sharing confidential data among healthcare providers.
2. Financial Services: Analyze financial data for risk management and fraud detection while keeping client information encrypted.
3. Ad Campaign Tracking: Create targeted ads and campaign insights while respecting user privacy through encrypted data analysis.
4. Predictive Maintenance: Enhance efficiency by performing predictive maintenance in the cloud while safeguarding sensitive data.
5. Biometrics: Develop user authentication applications without compromising identities.
6. Government Services: Digitize government services without relying on cloud providers’ trust.
Other Notable Players in the FHE Landscape:
* HELib: This powerful library from IBM provides efficient implementations of FHE schemes, making it easier for researchers and developers to experiment with and integrate FHE into their applications.
* OpenFHE: This open-source initiative aims to democratize access to FHE technology by fostering collaboration and sharing resources. By providing a platform for sharing FHE implementations, algorithms, and best practices, OpenFHE accelerates the adoption of FHE and its integration into real-world applications.
The Growing Demand for Education and Research
As FHE and privacy-preserving ML gain momentum, the demand for educational resources and courses is also rising. Universities and research institutions are actively offering courses and workshops on cryptographic techniques, secure computing, and privacy-preserving technologies, equipping students and professionals with the necessary knowledge and skills to navigate this evolving field.
Looking Ahead: Pushing the Boundaries
The future of FHE and privacy-preserving ML is bright, with ongoing research continuously pushing the boundaries of what is possible. Researchers are actively exploring new:
* FHE schemes: This involves developing more efficient and secure ways to perform computations on encrypted data.
* Optimisation techniques: This focuses on improving the performance and scalability of FHE algorithms, making them more practical for real-world applications.
* Applications: This includes exploring FHE’s potential in areas like federated learning, secure multi-party computation, and differential privacy, further expanding its reach and impact.
Conclusion:
FHE and Concrete ML represent a significant leap forward in privacy-preserving data analytics and ML. With the support of various platforms, frameworks, and initiatives, the adoption of FHE is poised for rapid growth. As we continue to invest in education, research, and collaboration, we can unlock the full potential of FHE and build a more secure and privacy-conscious digital ecosystem for the future.
*Remember: With FHE, even the most intricate calculations can remain hidden, like secrets whispered in a cryptographic breeze.*
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