Become TFHE-rs

1 Introduction

See the previous blog:

• Guide to fully homomorphic encryption based on [Discretized] Torus (1)
• Guide to fully homomorphic encryption based on [Discretized] Torus (2)
• TFHE - fully homomorphic encryption code analysis based on [Discretized] Torus

For open source code, see:

• https://github.com/zama-ai/tfhe-rs（Rust）

TFHE-rs is:

• TFHE (Fully Homomorphic Encryption over Torus) implemented in pure Rust.
• Supports Boolean operations and integer operations on encrypted data.
• Based on Learning With Errors (LWE) cryptographic primitives - resistant to quantum computers.
• Rust API, C API and client-side WASM API are provided.
• It is fully homomorphic and can handle messages with fixed precision numbers.
• Implemented Programmable Bootstrapping.

2. Key cryptographic concepts

In cryptography:

• The raw value is called message, or cleartext (original text).
• The encoded message is called plaintext.
• The encrypted plaintext is called ciphertext.

The core idea of ​​homomorphic encryption is to calculate the ciphertext without knowing the message in the ciphertext. If a scheme is fully homomorphic, it means that it can be used for plain text xxCiphertexte [ x ] e[x]$of\; x$$e\left[x\right]$ does the following operations:

• 1) Homomorphic single-variable function evaluation: $f(E[x])=E[f(x)]$
• 2) Same addition: $E\left[x\right]+Hey]\_\_=And[x+y]$
• 3) The same method: $E\left[x\right]\ast Hey]\_\_=And[x\ast y]$

3. TFHE-rs function

The basic functional process of TFHE-rs is:

• 1) Use security parameters to generate client key and server key.
  • Client key: used to encrypt and decrypt data. The client key must be kept secret.
  • server key: used to perform operations on ciphertext. The server key can be made public. Server key is also called evaluation key.
• 2) Use client key to encrypt plain text.
• 3) Use server key to perform homomorphic operations on ciphertext.
• 4) Use the client key to decrypt the result ciphertext to obtain the result plaintext.

References

[1] What is TFHE-rs?

FHE Series Blog

• Technical Exploration: Verifying FHE in RISC Zero - From Hiding to Proving: ZK Path of FHE Verification (1)
• Guide to fully homomorphic encryption based on [Discretized] Torus (1)
• Guide to fully homomorphic encryption based on [Discretized] Torus (2)
• TFHE - fully homomorphic encryption code analysis based on [Discretized] Torus
• Technology Exploration: Verifying FHE in RISC Zero—DevOps for RISC Zero Applications (2)
• Introduction to FHE