# 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.

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