Cryptographers rely on visualization to effectively communicate cryptographic constructions with one another. Visual frameworks such as constructive cryptography (TOSCA 2011), the joy of cryptography (online book) and state-separating proofs (SSPs, Asiacrypt 2018) are useful to communicate not only the construction, but also their proof visually by representing a cryptographic system as graphs. One SSP core feature is the re-use of code, e.g., a package of code might be used in a game...

We give the first construction of a fully black-box round-optimal secure multiparty computation (MPC) protocol in the plain model. Our protocol makes black-box use of a sub-exponentially secure two-message statistical sender private oblivious transfer (SSP-OT), which in turn can be based on (sub-exponential variants of) almost all of the standard cryptographic assumptions known to imply public-key cryptography.

Statistical sender privacy (SSP) is the strongest achievable security notion for two-message oblivious transfer (OT) in the standard model, providing statistical security against malicious receivers and computational security against semi-honest senders. In this work we provide a novel construction of SSP OT from the Decisional Diffie-Hellman (DDH) and the Learning Parity with Noise (LPN) assumptions achieving (asymptotically) optimal amortized communication complexity, i.e. it achieves rate...

Universally composable (UC) security is the most widely used framework for analyzing the security of cryptographic protocols. Many variants and simplifications of the framework have been proposed and developed, nonetheless, many practitioners find UC proofs to be both difficult to construct and understand. We remedy this situation by proposing a new framework for protocol security. We believe that our framework provides proofs that are both easier to write, but also more rigorous, and...

We construct a two-message oblivious transfer protocol with statistical sender privacy (SSP OT) based on the Learning Parity with Noise (LPN) Assumption and a standard Nisan-Wigderson style derandomization assumption. Beyond being of interest on their own, SSP OT protocols have proven to be a powerful tool toward minimizing the round complexity in a wide array of cryptographic applications from proofs systems, through secure computation protocols, to hard problems in statistical zero...

We propose a general framework for non-universal SNARKs. It contains (1) knowledge-sound and non-black-box any-simulation-extractable (ASE), (2) zero-knowledge and subversion-zero knowledge SNARKs for the well-known QAP, SAP, QSP, and QSP constraint languages that all by design have \emph{relatively} simple security proofs. The knowledge-sound zero-knowledge SNARK is similar to Groth's SNARK from EUROCRYPT 2016, except having fewer trapdoors, while the ASE subversion-zero knowledge SNARK...

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...

Machine-checked cryptography aims to reinforce confidence in the primitives and protocols that underpin all digital security. However, machine-checked proof techniques remain in practice difficult to apply to real-world constructions. A particular challenge is structured reasoning about complex constructions at different levels of abstraction. The State-Separating Proofs (SSP) methodology for guiding cryptographic proofs by Brzuska, Delignat-Lavaud, Fournet, Kohbrok and Kohlweiss...

The most efficient SNARKs (e.g., Groth, 2016) have a brittle and difficult-to-verify knowledge-soundness proof in the generic model, which makes it nontrivial to modify such SNARKs to, e.g., satisfy simulation-extractability or to implement some other language instead of QAP (Quadratic Arithmetic Program). We propose knowledge-sound and non-black-box tag-based strong any-simulation-extractable ($\tagSASE$) subversion-zero knowledge SNARKs for QAP that by design have a relatively simple...

Zero-knowledge SNARKs (zk-SNARKs) are non-interactive proof systems with short (i.e., independent of the size of the witness) and efficiently verifiable proofs. They elegantly resolve the juxtaposition of individual privacy and public trust, by providing an efficient way of demonstrating knowledge of secret information without actually revealing it. To this day, zk-SNARKs are widely deployed all over the planet and are used to keep alive a system worth billion of euros, namely the...