[Resource Topic] 2021/165: Composition with Knowledge Assumptions

Welcome to the resource topic for 2021/165

Title:
Composition with Knowledge Assumptions

Authors: Thomas Kerber, Aggelos Kiayias, Markulf Kohlweiss

Abstract:

Zero-knowledge succinct non-interactive arguments (zk-SNARKs) rely on knowledge assumptions for their security. Meanwhile, as the complexity and scale of cryptographic systems continues to grow, the composition of secure protocols is of vital importance. The current gold standards of composable security, the Universal Composability and Constructive Cryptography frameworks cannot capture knowledge assumptions, as their core proofs of composition prohibit white-box extraction. In this paper, we present a formal model allowing the composition of knowledge assumptions. Despite showing impossibility for the general case, we demonstrate the model’s usefulness when limiting knowledge assumptions to few instances of protocols at a time. We finish by providing the first instance of a simultaneously succinct and composable zk-SNARK, by using existing results within our framework.

ePrint: https://eprint.iacr.org/2021/165

Talk: https://www.youtube.com/watch?v=LuPgS94x0x4

Slides: https://iacr.org/submit/files/slides/2021/crypto/crypto2021/241/slides.pdf

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