2.6 KiB
What is TFHE-rs?
TFHE-rs is a pure Rust implementation of Fully Homomorphic Encryption over the Torus (TFHE) to perform Boolean and integer arithmetic on encrypted data.
TFHE-rs implements advanced TFHE features, empowering developers and researchers with fine-grained control over TFHE so that they can focus on high-level functionality without delving into low-level implementation.
TFHE-rs includes:
- Rust API: the primary API for working with TFHE-rs in Rust projects.
- C API: for developers who prefer to use C.
- Client-side WASM API: to integrate TFHE-rs functionalities into WebAssembly applications.
Key cryptographic concepts
TFHE is a Fully Homomorphic Encryption (FHE) scheme based on Learning With Errors (LWE), which is a secure cryptographic primitive against even quantum computers. The TFHE-rs library implements Zama’s variant of TFHE.
Homomorphic Encryption Basics
The basic elements of cryptography:
- Message (or Cleartext): raw values before encryption.
- Plaintext: encoded messages.
- Ciphertext: encrypted messages.
FHE allows to compute on ciphertexts without revealing the content of the messages. A scheme is fully homomorphic if it supports at least two of the following operations when evaluating any programs. (x is a plaintext and E[x] is the corresponding ciphertext):
- Homomorphic univariate function evaluation:
f(E[x]) = E[f(x)] - Homomorphic addition:
E[x] + E[y] = E[x + y] - Homomorphic multiplication:
E[x] * E[y] = E[x * y]
Zama's variant of TFHE
Zama's variant of TFHE is a fully homomorphic scheme that takes fixed-precision numbers as messages. It implements all homomorphic operations needed, such as addition and function evaluation via Programmable Bootstrapping.
Refer to the the preliminary whitepaper for more details.
Using TFHE-rs in Rust includes the following steps:
- Key generation: generate a pair of keys using secure parameters.
- Client key: used for encryption and decryption of data. This key must be kept secret.
- Server key (or Evaluation key): used for performing operations on encrypted data. This key could be public.
- Encryption: encrypt plaintexts using the client key to produce ciphertexts.
- Homomorphic operation: perform operations on ciphertexts using the server key.
- Decryption: decrypt the resulting ciphertexts back to plaintexts using the client key.
To understand more about FHE applications, see the 6-minute introduction to homomorphic encryption.