International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Composition with Knowledge Assumptions

Thomas Kerber , The University of Edinburgh & IOHK
Aggelos Kiayias , The University of Edinburgh & IOHK
Markulf Kohlweiss , The University of Edinburgh & IOHK
DOI: 10.1007/978-3-030-84259-8_13 (login may be required)
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Presentation: Slides
Conference: CRYPTO 2021
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.
Video from CRYPTO 2021
  title={Composition with Knowledge Assumptions},
  author={Thomas Kerber and Aggelos Kiayias and Markulf Kohlweiss},