## CryptoDB

### Alessandro Chiesa

#### Publications

**Year**

**Venue**

**Title**

2024

CRYPTO

STIR: Reed–Solomon Proximity Testing with Fewer Queries
Abstract

We present STIR (Shift To Improve Rate), a concretely efficient interactive oracle proof of proximity (IOPP) for Reed--Solomon codes that achieves the best known query complexity of any concretely efficient IOPP for this problem. Roughly, in order to achieve $\lambda$ bits of security, STIR has query complexity $O(\log d + \lambda \cdot \loglog d )$, while the popular FRI protocol (including variants based on conjectured security assumptions) has query complexity $O(\lambda \cdot \log d )$. STIR relies on a new technique for recursively reducing the degree of the function being tested while simultaneously improving the rate.
We provide an implementation of STIR compiled to a SNARK. Compared to FRI, our implementation achieves an improvement in argument size that ranges from $1.25\times$ to $2.46\times$ depending on the chosen parameters. For example, in order to achieve 128 bits of security for degree $2^{26}$ and rate $1/4$, STIR has argument size $114$~KiB, compared to $211$~KiB for FRI.

2024

TCC

zkSNARKs in the ROM with Unconditional UC-Security
Abstract

The universal composability (UC) framework is a “gold standard” for security in cryptography. UC-secure protocols achieve strong security guarantees against powerful adaptive adversaries, and retain these guarantees when used as part of larger protocols. Zero knowledge succinct non-interactive arguments of knowledge (zkSNARKs) are a popular cryptographic primitive that are often used within larger protocols deployed in dynamic environments, and so UC-security is a highly desirable, if not necessary, goal.
In this paper we prove that there exist zkSNARKs in the random oracle model (ROM) that unconditionally achieve UC-security. Here, “unconditionally” means that security holds against adversaries that make a bounded number of queries to the random oracle, but are otherwise computationally unbounded.
Prior work studying UC-security for zkSNARKs obtains transformations that rely on computational assumptions and, in many cases, lose most of the succinctness property of the zkSNARK. Moreover, these transformations make the resulting zkSNARK more expensive and complicated.
In contrast, we prove that widely used zkSNARKs in the ROM are UC-secure without modifications. We prove that the Micali construction, which is the canonical construction of a zkSNARK, is UC-secure. Moreover, we prove that the BCS construction, which many zkSNARKs deployed in practice are based on, is UC-secure. Our results confirm the intuition that these natural zkSNARKs do not need to be augmented to achieve UC-security, and give confidence that their use in larger real-world systems is secure.

2024

TCC

Untangling the Security of Kilian's Protocol: Upper and Lower Bounds
Abstract

Sigma protocols are elegant cryptographic proofs that have become a cornerstone of modern cryptography. A notable example is Schnorr's protocol, a zero-knowledge proof-of-knowledge of a discrete logarithm. Despite extensive research, the security of Schnorr's protocol in the standard model is not fully understood.
In this paper we study \emph{Kilian's protocol}, an influential public-coin interactive protocol that, while not a sigma protocol, shares striking similarities with sigma protocols. The first example of a succinct argument, Kilian's protocol is proved secure via \emph{rewinding}, the same idea used to prove sigma protocols secure. In this paper we show how, similar to Schnorr's protocol, a precise understanding of the security of Kilian's protocol remains elusive. We contribute new insights via upper bounds and lower bounds.
\begin{itemize}
\item \emph{Upper bounds.}
We establish the tightest known bounds on the security of Kilian's protocol in the standard model, via strict-time reductions and via expected-time reductions. Prior analyses are strict-time reductions that incur large overheads or assume restrictive properties of the PCP underlying Kilian's protocol.
\item \emph{Lower bounds.}
We prove that significantly improving on the bounds that we establish for Kilian's protocol would imply improving the security analysis of Schnorr's protocol beyond the current state-of-the-art (an open problem). This partly explains the difficulties in obtaining tight bounds for Kilian's protocol.
\end{itemize}

2024

TCC

Security Bounds for Proof-Carrying Data from Straightline Extractors
Abstract

Proof-carrying data (PCD) is a powerful cryptographic primitive that allows mutually distrustful parties to perform distributed computation in an efficiently verifiable manner. Real-world deployments of PCD have sparked keen interest within the applied community and industry.
Known constructions of PCD are obtained by recursively-composing SNARKs or related primitives. Unfortunately, known security analyses incur expensive blowups, which practitioners have disregarded as the analyses would lead to setting parameters that are prohibitively expensive.
In this work we study the concrete security of recursive composition, with the goal of better understanding how to reasonably set parameters for certain PCD constructions of practical interest. Our main result is that PCD obtained from SNARKs with \emph{straightline knowledge soundness} has essentially the same security as the underlying SNARK (i.e., recursive composition incurs essentially no security loss).
We describe how straightline knowledge soundness is achieved by SNARKs in several oracle models, which results in a highly efficient security analysis of PCD that makes black-box use of the SNARK's oracle (there is no need to instantiated the oracle to carry out the security reduction).
As a notable application, our work offers an idealized model that provides new, albeit heuristic, insights for the concrete security of \emph{recursive STARKs} used in blockchain systems. Our work could be viewed as partial evidence justifying the parameter choices for recursive STARKs made by practitioners.

2023

EUROCRYPT

Proof-Carrying Data From Arithmetized Random Oracles
Abstract

Proof-carrying data (PCD) is a powerful cryptographic primitive that allows mutually distrustful parties to perform distributed computation in an efficiently verifiable manner. Known constructions of PCD are obtained by recursively-composing SNARKs or related primitives. SNARKs with desirable properties such as transparent setup are constructed in the random oracle model. However, using such SNARKs to construct PCD requires heuristically instantiating the oracle and using it in a non-black-box way. Chen, Chiesa and Spooner [Eurocrypt'22] constructed SNARKs in the low-degree random oracle model, circumventing this issue, but instantiating their model in the real world appears difficult.
In this paper, we introduce a new model: the arithmetized random oracle model (AROM). We provide a plausible standard-model (software-only) instantiation of the AROM, and we construct PCD in the AROM, given only a standard-model collision-resistant hash function. Furthermore, our PCD construction is for arbitrary-depth compliance predicates. We obtain our PCD construction by showing how to construct SNARKs in the AROM for computations that query the oracle, given an accumulation scheme for oracle queries in the AROM. We then construct such an accumulation scheme for the AROM.
To prove the security of cryptographic constructs in the AROM, we give a non-trivial and efficient "lazy sampling" algorithm (a "stateful emulator") for the ARO up to some error. We obtain this construction by developing a toolkit for analyzing cryptographic constructions in the AROM, which uses algebraic query complexity techniques and the combinatorial nullstellensatz.

2023

CRYPTO

Lattice-Based Succinct Arguments for NP with Polylogarithmic-Time Verification
Abstract

The ideal argument system should offer small proof sizes in practice, succinct verification, and post-quantum security based on standard assumptions. However, so far, all known constructions fall short. Succinct argument systems which rely on the Merkle-hashing paradigm introduced by Kilian (STOC 92) suffer from large proof sizes in practice due to the use of generic cryptographic primitives. Popular alternatives, which obtain smaller proof sizes by exploiting the structure of homomorphic commitment schemes, either rely on quantum-insecure assumptions, or fail to provide succinct verification.
In this paper, we construct the first lattice-based succinct interactive argument system for NP statements with succinct verification that departs from the Merkle-hashing paradigm, and exploits the homomorphic properties of lattice-based commitments. For an arithmetic circuit with N gates, our construction achieves polylog(N) communication and polylog(N) verification time based on the hardness of the Ring Short- Integer-Solution (RSIS) problem.
The core technique in our construction is a delegation protocol built from commitment schemes based on leveled bilinear modules, a new notion that we deem of independent interest. We show that leveled bilinear modules can be realized from both pre-quantum and post-quantum cryptographic assumptions.

2022

EUROCRYPT

A PCP Theorem for Interactive Proofs and Applications
📺
Abstract

The celebrated PCP Theorem states that any language in NP can be decided via a verifier that reads O(1) bits from a polynomially long proof. Interactive oracle proofs (IOP), a generalization of PCPs, allow the verifier to interact with the prover for multiple rounds while reading a small number of bits from each prover message. While PCPs are relatively well understood, the power captured by IOPs (beyond $\NP$) has yet to be fully explored.
We present a generalization of the PCP theorem for interactive languages. We show that any language decidable by a k(n)-round IP has a k(n)-round public-coin IOP, where the verifier makes its decision by reading only O(1) bits from each (polynomially long) prover message and $O(1)$ bits from each of its own (random) messages to the prover.
Our result and the underlying techniques have several applications. We get a new hardness of approximation result for a stochastic satisfiability problem, we show IOP-to-IOP transformations that previously were known to hold only for IPs, and we formulate a new notion of PCPs (index-decodable PCPs) that enables us to obtain a commit-and-prove SNARK in the random oracle model for nondeterministic computations.

2022

EUROCRYPT

On Succinct Non-Interactive Arguments in Relativized Worlds
📺
Abstract

Succinct non-interactive arguments of knowledge (SNARKs) are cryptographic proofs with strong efficiency properties. Applications of SNARKs often involve proving computations that include the SNARK verifier, a technique called recursive composition. Unfortunately, SNARKs with desirable features such as a transparent (public-coin) setup are known only in the random oracle model (ROM). In applications this oracle must be heuristically instantiated and used in a non-black-box way.
In this paper we identify a natural oracle model, the low-degree random oracle model, in which there exist transparent SNARKs for all NP computations *relative to this oracle*. Informally, letting $O$ be a low-degree encoding of a random oracle, and assuming the existence of (standard-model) collision-resistant hash functions, there exist SNARKs relative to $O$ for all languages in $NP^{O}$. Such a SNARK can directly prove a computation about its own verifier.
To analyze this model, we introduce a more general framework, the *linear code random oracle model* (LCROM). We show how to obtain SNARKs in the LCROM for computations that query the oracle, given an *accumulation scheme* for oracle queries. Then we construct such an accumulation scheme for the special case of a low degree random oracle.

2022

EUROCRYPT

Zero-Knowledge IOPs with Linear-Time Prover and Polylogarithmic-Time Verifier
📺
Abstract

Interactive oracle proofs (IOPs) are a multi-round generalization of probabilistically checkable proofs that play a fundamental role in the construction of efficient cryptographic proofs.
We present an IOP that simultaneously achieves the properties of zero knowledge, linear-time proving, and polylogarithmic-time verification. We construct a zero-knowledge IOP where, for the satisfiability of an $N$-gate arithmetic circuit over any field of size $\Omega(N)$, the prover uses $O(N)$ field operations and the verifier uses $\polylog(N)$ field operations (with proof length $O(N)$ and query complexity $\polylog(N)$). Polylogarithmic verification is achieved in the holographic setting for every circuit (the verifier has oracle access to a linear-time-computable encoding of the circuit whose satisfiability is being proved).
Our result implies progress on a basic goal in the area of efficient zero knowledge. Via a known transformation, we obtain a zero knowledge argument system where the prover runs in linear time and the verifier runs in polylogarithmic time; the construction is plausibly post-quantum and only makes a black-box use of lightweight cryptography (collision-resistant hash functions).

2022

EUROCRYPT

Gemini: elastic SNARKs for diverse environments
📺
Abstract

We introduce a new class of succinct arguments, that we call elastic. Elastic SNARKs allow the prover to allocate different resources (such as memory and time) depending on the execution environment and the statement to prove. The resulting output is independent of the prover’s configuration. To study elastic SNARKs, we extend the streaming paradigm of [Block et al., TCC’20]. We provide a definitional framework for elastic polynomial interactive oracle proofs for R1CS instances and design a compiler which transforms an elastic PIOP into a preprocessing argument system that supports streaming or random access to its inputs. Depending on the configuration, the prover will choose different trade-offs for time (either linear, or quasilinear) and memory (either linear, or logarithmic).
We prove the existence of elastic SNARKS by presenting Gemini, a novel FFT-free preprocessing argument. We prove its security and develop a proof-of-concept implementation in Rust based on the arkworks framework. We provide benchmarks for large R1CS instances of tens of billions of gates on a single machine.

2022

TCC

A Toolbox for Barriers on Interactive Oracle Proofs
Abstract

Interactive oracle proofs (IOPs) are a proof system model that combines features of interactive proofs (IPs) and probabilistically checkable proofs (PCPs). IOPs have prominent applications in complexity theory and cryptography, most notably to constructing succinct arguments.
In this work, we study the limitations of IOPs, as well as their relation to those of PCPs. We present a versatile toolbox of IOP-to-IOP transformations containing tools for: (i) length and round reduction; (ii) improving completeness; and (iii) derandomization.
We use this toolbox to establish several barriers for IOPs:
\begin{itemize}
\item Low-error IOPs can be transformed into low-error PCPs. In other words, interaction can be used to construct low-error PCPs; alternatively, low-error IOPs are as hard to construct as low-error PCPs. This relates IOPs to PCPs in the regime of the sliding scale conjecture for inverse-polynomial soundness error.
\item Limitations of quasilinear-size IOPs for 3SAT with small soundness error.
\item Limitations of IOPs where query complexity is much smaller than round complexity.
\item Limitations of binary-alphabet constant-query IOPs.
\end{itemize}
We believe that our toolbox will prove useful to establish additional barriers beyond our work.

2022

JOFC

Succinct Non-Interactive Arguments via Linear Interactive Proofs
Abstract

Succinct non-interactive arguments (SNARGs) enable verifying NP statements with lower complexity than required for classical NP verification. Traditionally, the focus has been on minimizing the length of such arguments; nowadays, researchers have focused also on minimizing verification time, by drawing motivation from the problem of delegating computation. A common relaxation is a preprocessing SNARG, which allows the verifier to conduct an expensive offline phase that is independent of the statement to be proven later. Recent constructions of preprocessing SNARGs have achieved attractive features: they are publicly-verifiable, proofs consist of only O (1) encrypted (or encoded) field elements, and verification is via arithmetic circuits of size linear in the NP statement. Additionally, these constructions seem to have “escaped the hegemony” of probabilistically-checkable proofs (PCPs) as a basic building block of succinct arguments. We present a general methodology for the construction of preprocessing $$\text{ SNARG } $$ SNARG s, as well as resulting new efficiency features. Our contribution is threefold: (1) We introduce and study a natural extension of the interactive proof model that considers algebraically-bounded provers; this new setting is analogous to the common study of algebraically-bounded “adversaries” in other fields, such as pseudorandomness and randomness extraction. More concretely, in this work we focus on linear (or affine) provers, and provide several constructions of (succinct two-message) linear interactive proofs (LIPs) for NP. Our constructions are based on general transformations applied to both linear PCPs (LPCPs) and traditional “unstructured” PCPs. (2) We give conceptually simple cryptographic transformations from LIPs to preprocessing SNARGs, whose security can be based on different forms of linear targeted malleability (implied by previous knowledge assumptions). Our transformations convert arbitrary (two-message) LIPs into designated-verifier SNARGs, and LIPs with degree-bounded verifiers into publicly-verifiable SNARGs. We also extend our methodology to obtain zero-knowledge LIPs and SNARGs. Our techniques yield SNARGs of knowledge and thus can benefit from known recursive composition and bootstrapping techniques. (3) Following this methodology, we exhibit several constructions achieving new efficiency features, such as “single-ciphertext preprocessing SNARGs.” We also offer a new perspective on existing constructions of preprocessing SNARGs, revealing a direct connection of these to LPCPs and LIPs.

2021

CRYPTO

Subquadratic SNARGs in the Random Oracle Model
📺
Abstract

In a seminal work, Micali (FOCS 1994) gave the first succinct non-interactive argument (SNARG) in the random oracle model (ROM). The construction combines a PCP and a cryptographic commitment, and has several attractive features: it is plausibly post-quantum; it can be heuristically instantiated via lightweight cryptography; and it has a transparent (public-coin) parameter setup. However, it also has a significant drawback: a large argument size.
In this work, we provide a new construction that achieves a smaller argument size. This is the first progress on the Micali construction since it was introduced over 25 years ago.
A SNARG in the ROM is (t,ε)-secure if every t-query malicious prover can convince the verifier of a false statement with probability at most ε. For (t,ε)-security, the argument size of all known SNARGs in the ROM (including Micali's) is Õ((log (t/ε))^2) bits, *even* if one were to rely on conjectured probabilistic proofs well beyond current techniques. In practice, these costs lead to SNARGs that are much larger than constructions based on other (pre-quantum and costly) tools. This has led many to believe that SNARGs in the ROM are inherently quadratic.
We show that this is not the case. We present a SNARG in the ROM with a sub-quadratic argument size: Õ(log (t/ε) * log t). Our construction relies on a strong soundness notion for PCPs and a weak binding notion for commitments. We hope that our work paves the way for understanding if a linear argument size, that is O(log (t/ε)), is achievable in the ROM.

2021

CRYPTO

Sumcheck Arguments and their Applications
📺
Abstract

We introduce a class of interactive protocols, which we call *sumcheck arguments*, that establishes a novel connection between the sumcheck protocol (Lund et al. JACM 1992) and folding techniques for Pedersen commitments (Bootle et al. EUROCRYPT 2016).
Informally, we consider a general notion of bilinear commitment over modules, and show that the sumcheck protocol applied to a certain polynomial associated with the commitment scheme yields a succinct argument of knowledge for openings of the commitment. Building on this, we additionally obtain succinct arguments for the NP-complete language R1CS over certain rings.
Sumcheck arguments enable us to recover as a special case numerous prior works in disparate cryptographic settings (such as discrete logarithms, pairings, RSA groups, lattices), providing one abstract framework to understand them all. Further, we answer open questions raised in prior works, such as obtaining a lattice-based succinct argument from the SIS assumption for satisfiability problems over rings.

2021

CRYPTO

Proof-Carrying Data without Succinct Arguments
📺
Abstract

Proof-carrying data (PCD) is a powerful cryptographic primitive that enables mutually distrustful parties to perform distributed computations that run indefinitely. Known approaches to construct PCD are based on succinct non-interactive arguments of knowledge (SNARKs) that have a succinct verifier or a succinct accumulation scheme.
In this paper we show how to obtain PCD without relying on SNARKs. We construct a PCD scheme given any non-interactive argument of knowledge (e.g., with linear-size arguments) that has a *split accumulation scheme*, which is a weak form of accumulation that we introduce.
Moreover, we construct a transparent non-interactive argument of knowledge for R1CS whose split accumulation is verifiable via a (small) *constant number of group and field operations*. Our construction is proved secure in the random oracle model based on the hardness of discrete logarithms, and it leads, via the random oracle heuristic and our result above, to concrete efficiency improvements for PCD.
Along the way, we construct a split accumulation scheme for Hadamard products under Pedersen commitments and for a simple polynomial commitment scheme based on Pedersen commitments.
Our results are supported by a modular and efficient implementation.

2021

TCC

Tight Security Bounds for Micali’s SNARGs
📺
Abstract

Succinct non-interactive arguments (SNARGs) in the random oracle model (ROM) have several attractive features: they are plausibly post-quantum; they can be heuristically instantiated via lightweight cryptography; and they have a transparent (public-coin) parameter setup.
The canonical construction of a SNARG in the ROM is due to Micali (FOCS 1994), who showed how to use a random oracle to compile any probabilistically checkable proof (PCP) with sufficiently-small soundness error into a corresponding SNARG. Yet, while Micali's construction is a seminal result, it has received little attention in terms of analysis in the past 25 years.
In this paper, we observe that prior analyses of the Micali construction are not tight and then present a new analysis that achieves tight security bounds. Our result enables reducing the random oracle's output size, and obtain corresponding savings in concrete argument size.
Departing from prior work, our approach relies on precisely quantifying the cost for an attacker to find several collisions and inversions in the random oracle, and proving that any PCP with small soundness error withstands attackers that succeed in finding a small number of collisions and inversions in a certain tree-based information-theoretic game.

2020

EUROCRYPT

Marlin: Preprocessing zkSNARKs with Universal and Updatable SRS
📺
Abstract

We present a general methodology to construct preprocessing zkSNARKs where the structured reference string (SRS) is universal and updatable. This exploits a novel application of *holographic* IOPs, a natural generalization of holographic PCPs [Babai et al., STOC 1991].
We use our methodology to obtain a preprocessing zkSNARK where the SRS has linear size and arguments have constant size. Our construction improves on Sonic [Maller et al., CCS 2019], the prior state of the art in this setting, in all efficiency parameters: proving is an order of magnitude faster and verification is twice as fast, even with smaller SRS size and argument size. Our construction is most efficient when instantiated in the algebraic group model (also used by Sonic), but we also demonstrate how to realize it under concrete knowledge assumptions.
The core of our zkSNARK is a new holographic IOP for rank-1 constraint satisfiability (R1CS), which is the first to achieve linear proof length and constant query complexity (among other efficiency features).

2020

EUROCRYPT

Fractal: Post-Quantum and Transparent Recursive Proofs from Holography
📺
Abstract

We present a new methodology to efficiently realize recursive composition of succinct non-interactive arguments of knowledge (SNARKs). Prior to this work, the only known methodology relied on pairing-based SNARKs instantiated on cycles of pairing-friendly elliptic curves, an expensive algebraic object. Our methodology does not rely on any special algebraic objects and, moreover, achieves new desirable properties: it is post-quantum and it is transparent (the setup is public coin).
We exploit the fact that recursive composition is simpler for SNARKs with preprocessing, and the core of our work is obtaining a preprocessing zkSNARK for rank-1 constraint satisfiability (R1CS) that is post-quantum and transparent. We obtain this latter by establishing a connection between holography and preprocessing in the random oracle model, and then constructing a holographic proof for R1CS.
We experimentally validate our methodology, demonstrating feasibility in practice.

2020

TCC

Proof-Carrying Data from Accumulation Schemes
📺
Abstract

Recursive proof composition has been shown to lead to powerful primitives such as incrementally-verifiable computation (IVC) and proof-carrying data (PCD). All existing approaches to recursive composition take a succinct non-interactive argument of knowledge (SNARK) and use it to prove a statement about its own verifier. This technique requires that the verifier run in time sublinear in the size of the statement it is checking, a strong requirement that restricts the class of SNARKs from which PCD can be built. This in turn restricts the efficiency and security properties of the resulting scheme.
Bowe, Grigg, and Hopwood (ePrint 2019/1021) outlined a novel approach to recursive composition, and applied it to a particular SNARK construction which does *not* have a sublinear-time verifier. However, they omit details about this approach and do not prove that it satisfies any security property. Nonetheless, schemes based on their ideas have already been implemented in software.
In this work we present a collection of results that establish the theoretical foundations for a generalization of the above approach. We define an *accumulation scheme* for a non-interactive argument, and show that this suffices to construct PCD, even if the argument itself does not have a sublinear-time verifier. Moreover we give constructions of accumulation schemes for SNARKs, which yield PCD schemes with novel efficiency and security features.

2020

TCC

Linear-Time Arguments with Sublinear Verification from Tensor Codes
📺
Abstract

Minimizing the computational cost of the prover is a central goal in the area of succinct arguments. In particular, it remains a challenging open problem to construct a succinct argument where the prover runs in linear time and the verifier runs in polylogarithmic time.
We make progress towards this goal by presenting a new linear-time probabilistic proof. For any fixed ? > 0, we construct an interactive oracle proof (IOP) that, when used for the satisfiability of an N-gate arithmetic circuit, has a prover that uses O(N) field operations and a verifier that uses O(N^?) field operations. The sublinear verifier time is achieved in the holographic setting for every circuit (the verifier has oracle access to a linear-size encoding of the circuit that is computable in linear time).
When combined with a linear-time collision-resistant hash function, our IOP immediately leads to an argument system where the prover performs O(N) field operations and hash computations, and the verifier performs O(N^?) field operations and hash computations (given a short digest of the N-gate circuit).

2020

TCC

Barriers for Succinct Arguments in the Random Oracle Model
📺
Abstract

We establish barriers on the efficiency of succinct arguments in the random oracle model. We give evidence that, under standard complexity assumptions, there do not exist succinct arguments where the argument verifier makes a small number of queries to the random oracle.
The new barriers follow from new insights into how probabilistic proofs play a fundamental role in constructing succinct arguments in the random oracle model.
*IOPs are necessary for succinctness.*
We prove that any succinct argument in the random oracle model can be transformed into a corresponding interactive oracle proof (IOP). The query complexity of the IOP is related to the succinctness of the argument.
*Algorithms for IOPs.*
We prove that if a language has an IOP with good soundness relative to query complexity, then it can be decided via a fast algorithm with small space complexity.
By combining these results we obtain barriers for a large class of deterministic and non-deterministic languages. For example, a succinct argument for 3SAT with few verifier queries implies an IOP with good parameters, which in turn implies a fast algorithm for 3SAT that contradicts the Exponential-Time Hypothesis.
We additionally present results that shed light on the necessity of several features of probabilistic proofs that are typically used to construct succinct arguments, such as holography and state restoration soundness. Our results collectively provide an explanation for "why" known constructions of succinct arguments have a certain structure.

2019

EUROCRYPT

Aurora: Transparent Succinct Arguments for R1CS
Abstract

We design, implement, and evaluate a zero knowledge succinct non-interactive argument (SNARG) for Rank-1 Constraint Satisfaction (R1CS), a widely-deployed NP language undergoing standardization. Our SNARG has a transparent setup, is plausibly post-quantum secure, and uses lightweight cryptography. A proof attesting to the satisfiability of n constraints has size $$O(\log ^2 n)$$O(log2n); it can be produced with $$O(n \log n)$$O(nlogn) field operations and verified with O(n). At 128 bits of security, proofs are less than $${250}\,\mathrm{kB}$$250kB even for several million constraints, more than $$10{\times }$$10× shorter than prior SNARGs with similar features.A key ingredient of our construction is a new Interactive Oracle Proof (IOP) for solving a univariate analogue of the classical sumcheck problem [LFKN92], originally studied for multivariate polynomials. Our protocol verifies the sum of entries of a Reed–Solomon codeword over any subgroup of a field.We also provide $$\texttt {libiop}$$libiop, a library for writing IOP-based arguments, in which a toolchain of transformations enables programmers to write new arguments by writing simple IOP sub-components. We have used this library to specify our construction and prior ones, and plan to open-source it.

2019

TCC

Succinct Arguments in the Quantum Random Oracle Model
Abstract

Succinct non-interactive arguments (SNARGs) are highly efficient certificates of membership in non-deterministic languages. Constructions of SNARGs in the random oracle model are widely believed to be post-quantum secure, provided the oracle is instantiated with a suitable post-quantum hash function. No formal evidence, however, supports this belief.In this work we provide the first such evidence by proving that the SNARG construction of Micali is unconditionally secure in the quantum random oracle model. We also prove that, analogously to the classical case, the SNARG inherits the zero knowledge and proof of knowledge properties of the PCP underlying the Micali construction. We thus obtain the first zero knowledge SNARG of knowledge (zkSNARK) that is secure in the quantum random oracle model.Our main tool is a new lifting lemma that shows how, for a rich class of oracle games, we can generically deduce security against quantum attackers by bounding a natural classical property of these games. This means that in order to prove our theorem we only need to establish classical properties about the Micali construction. This approach not only lets us prove post-quantum security but also enables us to prove explicit bounds that are tight up to small factors.We additionally use our techniques to prove that SNARGs based on interactive oracle proofs (IOPs) with round-by-round soundness are unconditionally secure in the quantum random oracle model. This result establishes the post-quantum security of many SNARGs of practical interest.

2019

TCC

Linear-Size Constant-Query IOPs for Delegating Computation
Abstract

We study the problem of delegating computations via interactive proofs that can be probabilistically checked. Known as interactive oracle proofs (IOPs), these proofs extend probabilistically checkable proofs (PCPs) to multi-round protocols, and have received much attention due to their application to constructing cryptographic proofs (such as succinct non-interactive arguments). The relevant complexity measures for IOPs in this context are prover and verifier time, and query complexity.We construct highly efficient IOPs for a rich class of nondeterministic algebraic computations, which includes succinct versions of arithmetic circuit satisfiability and rank-one constraint system (R1CS) satisfiability. For a time-T computation, we obtain prover arithmetic complexity $$O(T \log T)$$ and verifier complexity polylog(T). These IOPs are the first to simultaneously achieve the state of the art in prover complexity, due to [14], and in verifier complexity, due to [7]. We also improve upon the query complexity of both schemes.The efficiency of our prover is a result of our highly optimized proof length; in particular, ours is the first construction that simultaneously achieves linear-size proofs and polylogarithmic-time verification, regardless of query complexity.

#### Program Committees

- Eurocrypt 2024
- Crypto 2019
- Eurocrypt 2018
- TCC 2017

#### Coauthors

- Gal Arnon (3)
- Eli Ben-Sasson (8)
- Iddo Bentov (1)
- Amey Bhangale (1)
- Nir Bitansky (4)
- Jonathan Bootle (5)
- Benedikt Bünz (2)
- Ran Canetti (1)
- Megan Chen (2)
- Alessandro Chiesa (35)
- Marcel Dall'Agnol (1)
- Giacomo Fenzi (2)
- Michael A. Forbes (1)
- Ariel Gabizon (3)
- Daniel Genkin (2)
- Lior Goldberg (1)
- Shafi Goldwasser (1)
- Matthew Green (1)
- Jens Groth (1)
- Ziyi Guan (2)
- Tom Gur (2)
- Matan Hamilis (1)
- Yuncong Hu (2)
- Yuval Ishai (2)
- Wei-Kai Lin (1)
- Huijia Lin (1)
- Jingcheng Liu (1)
- Siqi Liu (1)
- Mary Maller (1)
- Peter Manohar (1)
- Peihan Miao (1)
- Ian Miers (1)
- Pratyush Mishra (4)
- Jack O'Connor (1)
- Dev Ojha (1)
- Michele Orrù (1)
- Rafail Ostrovsky (2)
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