Lova is joint work with Duc Tu Pham (ENS Paris), Ngoc Khanh Nguyen (King’s College London), and Giacomo Fenzi (EPFL), and appears at Asiacrypt'24.

Our goal: IVC from lattices

Incrementally verifiable computation (IVC) is a cryptographic primitive that allows a long (possibly infinite) computation to be run, such that correctness of the state of the computation can be efficiently verified at any point. IVC and its generalisation, proof-carrying data (PCD), have found numerous applications in succinct blockchains, verifiable delay functions, SNARKs for machine computations, and more.

Fully Homomorphic Encryption (FHE) is seeing increasing real-world deployment to protect data in use by allowing computation over encrypted data. However, the same malleability that enables homomorphic computations also raises integrity issues, which have so far been mostly overlooked. While FHE’s lack of integrity has obvious implications for correctness, it also has severe implications for confidentiality: a malicious server can leverage the lack of integrity to carry out interactive key-recovery attacks. As a result, virtually all FHE schemes and applications assume an honest-but-curious server that does not deviate from the protocol. In practice, however, this assumption is insufficient for a wide range of deployment scenarios. While there has been work that aims to address this gap, these have remained isolated efforts considering only aspects of the overall problem and fail to fully address the needs and characteristics of modern FHE schemes and applications.