Paper 2026/1127

Verifiable Bootstrapping from Lattice-based Folding

Louis Tremblay Thibault, Zama, École de technologie supérieure

Abstract

We explicitly construct and benchmark the first lattice-based IVC scheme from folding. The scheme supports customizable constraint systems over rings which we exploit to obtain proofs of correct execution of an FHE bootstrapping, a critical component of verifiable FHE. Notably and of independent interest, we introduce a novel CCS relation capable of performing automorphism stability checks which yields better expressivity for CCS over rings. We use this new relation to arithmetize the folding scheme verifier as well as TFHE's bootstrapping operation, and measure the performance of our folding scheme implementation on this arithmetization. Benchmarks indicate smaller proofs compared to the state of the art at the cost of a sharp increase in prover and verifier time. Lastly, we consider the security of folding-based IVC schemes with a super-constant number of recursive rounds and give an argument for the knowledge soundness of our construction in the ROM. Our work also discusses and highlights key open questions for future work, such as the design of hash functions over rings that permit efficient arithmetizations.