Error-Simulatable Sanitization for TFHE and Applications

Nigel P. Smart; Michael Walter

Paper 2025/275

Error-Simulatable Sanitization for TFHE and Applications

Nigel P. Smart

, KU Leuven, Zama

Michael Walter

, Zama

Abstract

We show that the randomized TFHE bootstrapping technique of Bourse and Izabechéne provides a form of sanitization which is error-simulatable. This means that the randomized bootstrap can be used not only for sanitization of ciphertexts (i.e. to hide the function that has been computed), but that it can also be used in server-assisted threshold decryption. Thus we extend the server-assisted threshold decryption method of Passelégue and Stehlé (ASIACRYPT '24) to FHE schemes which have small ciphertext modulus (such as TFHE). In addition the error-simulatable sanitization enables us to obtain FuncCPA security for TFHE essentially for free.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Preprint.
Keywords: Multi-Party Computation Fully Homomorphic Encryption
Contact author(s): nigel @ zama ai
michael walter @ zama ai
History: 2025-02-18: approved; 2025-02-18: received; See all versions
Short URL: https://ia.cr/2025/275
License: CC BY-SA

BibTeX

@misc{cryptoeprint:2025/275,
      author = {Nigel P. Smart and Michael Walter},
      title = {Error-Simulatable Sanitization for {TFHE} and Applications},
      howpublished = {Cryptology {ePrint} Archive, Paper 2025/275},
      year = {2025},
      url = {https://eprint.iacr.org/2025/275}
}