SSProve: A Foundational Framework for Modular Cryptographic Proofs in Coq

Philipp G. Haselwarter, Exequiel Rivas, Antoine Van Muylder, Théo Winterhalter, Carmine Abate, Nikolaj Sidorenco, Cǎtǎlin Hriţcu, Kenji Maillard, Bas Spitters

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

4 Citations (Scopus)

Abstract

State-separating proofs (SSP) is a recent methodology for structuring game-based cryptographic proofs in a modular way, by using algebraic laws to exploit the modular structure of composed protocols. While promising, this methodology was previously not fully formalized and came with little tool support. We address this by introducing SSProve, the first general verification framework for machine-checked state-separating proofs. SSProve combines high-level modular proofs about composed protocols, as proposed in SSP, with a probabilistic relational program logic for formalizing the lower-level details, which together enable constructing machine-checked cryptographic proofs in the Coq proof assistant. Moreover, SSProve is itself fully formalized in Coq, including the algebraic laws of SSP, the soundness of the program logic, and the connection between these two verification styles.To illustrate SSProve, we use it to mechanize the simple security proofs of ElGamal and pseudo-random-function-based encryption. We also validate the SSProve approach by conducting two more substantial case studies: First, we mechanize an SSP security proof of the key encapsulation mechanism-data encryption mechanism (KEM-DEM) public key encryption scheme, which led to the discovery of an error in the original paper proof that has since been fixed. Second, we use SSProve to formally prove security of the sigma-protocol zero-knowledge construction, and we moreover construct a commitment scheme from a sigma-protocol to compare with a similar development in CryptHOL. We instantiate the security proof for sigma-protocols to give concrete security bounds for Schnorr's sigma-protocol.

Original languageEnglish
Article number15
JournalACM Transactions on Programming Languages and Systems
Volume45
Issue3
Pages (from-to)61
ISSN0164-0925
DOIs
Publication statusPublished - Jul 2023

Keywords

  • formal verification
  • game-based proofs
  • High-assurance cryptography
  • machine-checked proofs
  • modular proofs
  • probabilistic relational program logic
  • state-separating proofs

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