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8,503 results · page 261 of 355
Sanjam Garg, Mohammad Hajiabadi, Mohammad Mahmoody, Ameer Mohammed
No abstract is available for this record.
Stephan Krenn, Thomas Lorünser, Anja Salzer, Christoph Striecks
No abstract is available for this record.
Yael Tauman Kalai, Dakshita Khurana, Amit Sahai
No abstract is available for this record.
Yuncong Zhang, Long Yu, Zhen Liu, Zhiqiang Liu · 5 authors
No abstract is available for this record.
Stefan Dziembowski, Lisa Eckey, Sebastian Faust
We introduce FairSwap -- an efficient protocol for fair exchange of digital goods using smart contracts. A fair exchange protocol allows a sender S to sell a digital commodity x for a fixed price p to a receiver R. The protocol is said to be secure if R only pays if he receives the correct x. Our solution guarantees fairness by relying on smart contracts executed over decentralized cryptocurrencies, where the contract takes the role of an external judge that completes the exchange in case of disagreement. While in the past there have been several proposals for building fair exchange protocols over cryptocurrencies, our solution has two distinctive features that makes it particular attractive when users deal with large commodities. These advantages are: (1) minimizing the cost for running the smart contract on the blockchain, and (2) avoiding expensive cryptographic tools such as zero-knowledge proofs. In addition to our new protocols, we provide formal security definitions for smart contract based fair exchange, and prove security of our construction. Finally, we illustrate several applications of our basic protocol and evaluate practicality of our approach via a prototype implementation for fairly selling large files over the cryptocurrency Ethereum.
Seongseop Kim, David J. Wu
Non-interactive zero-knowledge (NIZK) proofs are fundamental to modern cryptography. Numerous NIZK constructions are known in both the random oracle and the common reference string (CRS) models. In the CRS model, there exist constructions from several classes of cryptographic assumptions such as trapdoor permutations, pairings, and indistinguishability obfuscation. However, at the time of the initial publication of this work, we did not have constructions of NIZKs from standard lattice assumptions. In this work, we take an initial step toward constructing multi-theorem NIZKs for general $$\mathsf {NP}$$ languages from standard lattice assumptions by considering a relaxation to the preprocessing model and a new model we call the designated-prover model. In the preprocessing model, a setup algorithm generates secret proving and verification keys for the prover and the verifier, respectively. In the designated-prover model, the proving key is secret, but the verification key is public. In both settings, the proving key is used to construct proofs and the verification key is used to check proofs. Finally, in the multi-theorem setting, both the proving and verification keys should be reusable for an unbounded number of theorems without compromising soundness or zero-knowledge. Previous constructions of NIZKs in the preprocessing model that rely on weaker assumptions like one-way functions or oblivious transfer are only secure in a single-theorem setting. Thus, constructing multi-theorem NIZKs in these relaxed models does not seem to be inherently easier than constructing them in the CRS model. In this work, we first construct a multi-theorem preprocessing NIZK argument from context-hiding homomorphic signatures. In fact, the construction is a designated-prover NIZK. We also show that using homomorphic commitments, we can get statistically sound proofs in the preprocessing and designated-prover models. Together with lattice-based instantiations of homomorphic signatures and commitments, we obtain the first multi-theorem NIZKs in the preprocessing and designated-prover models from standard lattice assumptions. Finally, we show how to generalize our construction to obtain a universally composable NIZK (UC-NIZK) in the preprocessing model from standard lattice assumptions. Our UC-NIZK relies on a simple preprocessing protocol based on a new primitive we call blind homomorphic signatures.
Carsten Baum, Huang Lin, Sabine Oechsner
No abstract is available for this record.
Ai Ishida, Yusuke Sakai, Keita Emura, Goichiro Hanaoka · 5 authors
No abstract is available for this record.
Yupeng Zhang
We study the problem of argument systems, where a computationally weak verifier outsources the execution of a computation to a powerful but untrusted prover, while being able to validate that the result was computed correctly through a proof generated by the prover. In addition, the zero-knowledge property guarantees that proof leaks no information about the potential secret input from the prover. Existing efficient zero-knowledge arguments with sublinear verification time require an expensive preprocessing phase that depends on a particular computation, and incur big overhead on the prover time and prover memory consumption. This thesis proposes new constructions for zero-knowledge arguments that overcome the above problems. The new constructions require only a one time preprocessing and can be used to validate any computations later. They also reduce the overhead on the prover time and memory by orders of magnitude. We apply our new constructions to build a verifiable database system and verifiable RAM programs, leading to significant improvements over prior work.
Fucai Luo, Kunpeng Wang
No abstract is available for this record.
Sharon Goldberg, Leonid Reyzin, Omar Sagga, Foteini Baldimtsi
In many applications, it is important to verify that an RSA public key (N; e) speci es a \npermutation over the entire space ZN, in order to prevent attacks due to adversarially-generated \npublic keys. We design and implement a simple and e cient noninteractive zero-knowledge \nprotocol (in the random oracle model) for this task. Applications concerned about adversarial \nkey generation can just append our proof to the RSA public key without any other modi cations \nto existing code or cryptographic libraries. Users need only perform a one-time veri cation of \nthe proof to ensure that raising to the power e is a permutation of the integers modulo N. For \ntypical parameter settings, the proof consists of nine integers modulo N; generating the proof \nand verifying it both require about nine modular exponentiations. \nWe extend our results beyond RSA keys and also provide e cient noninteractive zero- \nknowledge proofs for other properties of N, which can be used to certify that N is suitable \nfor the Paillier cryptosystem, is a product of two primes, or is a Blum integer. As compared to \nthe recent work of Auerbach and Poettering (PKC 2018), who provide two-message protocols for \nsimilar languages, our protocols are more e cient and do not require interaction, which enables \na broader class of applications.
Melissa Chase, Yevgeniy Dodis, Yuval Ishai, Daniel Kraschewski · 7 authors
We consider the problem of Non-Interactive Two-Party Secure Computation (NISC), where Rachel wishes to publish an encryption of her input x, in such a way that any other party, who holds an input y, can send her a single message which conveys to her the value f(x, y), and nothing more. We demand security against malicious parties. While such protocols are easy to construct using garbled circuits and general non-interactive zero-knowledge proofs, this approach inherently makes a non-black-box use of the underlying cryptographic primitives and is infeasible in practice.
Ruinian Li, Yinhao Xiao, Cheng Zhang, Tianyi Song · 5 authors
Privacy in online applications has drawn tremendous attention in recent years. With the development of cloud-based applications, protecting users' privacy while guaranteeing the expected service from the server has become a significant issue. This paper surveyed the most popular cryptographic algorithms in privacy-preserving online applications to provide a tutorial-like introduction to researchers in this area. Specifically, this paper focuses on introduction to homomorphic encryption, secret sharing, secure multi-party computation and zero-knowledge proof.
Georg Fuchsbauer, Michele Orrù
While non-interactive zero-knowledge (NIZK) proofs require trusted parameters, Groth, Ostrovsky and Sahai constructed non-interactive witness-indistinguishable (NIWI) proofs without any setup; they called their scheme a non-interactive zap. More recently, Bellare, Fuchsbauer and Scafuro investigated the security of NIZK in the face of parameter subversion and observe that NI zaps provide subversion-resistant soundness and WI.
Rafail Ostrovsky, Giuseppe Persiano, Daniele Venturi, Ivan Visconti
No abstract is available for this record.
Zhengjun Cao, Lihua Liu
No abstract is available for this record.
Navid Alamati, Chris Peikert, Noah Stephens-Davidowitz
No abstract is available for this record.
Zvika Brakerski, Nico Döttling
No abstract is available for this record.
Pavel Hubáček, Alon Rosen, Margarita Vald
We present an unconditional transformation from any honest-verifier statistical zero-knowledge (HVSZK) protocol to standard SZK that preserves round complexity and efficiency of both the verifier and the prover. This improves over currently known transformations, which either rely on some computational assumptions or introduce significant computational overhead. Our main conceptual contribution is the introduction of instance-dependent SZK proofs for NP, which serve as a building block in our transformation. Instance-dependent SZK for NP can be constructed unconditionally based on instance-dependent commitment schemes of Ong and Vadhan (TCC’08).
Kang Li, Rupeng Yang, Man Ho Au, Qiuliang Xu
No abstract is available for this record.
Lee Klingler
In joint work with Rainer Steinwandt and Dominique Unruh, we look at how the notion of perfect zero-knowledge proof leads to an assumption about probabilistic Turing machines. We prove a theorem in commutative algebra which shows that this assumption is not valid.
Ben Berger, Zvika Brakerski
No abstract is available for this record.
Georg Fuchsbauer, Eike Kiltz, Julian Loss
No abstract is available for this record.
Eli Ben‐Sasson, Alessandro Chiesa, Michael Riabzev, Nicholas Spooner · 6 authors
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 \(O(\log ^2 n)\); it can be produced with \(O(n \log n)\) field operations and verified with O(n). At 128 bits of security, proofs are less than \({250}\,\mathrm{kB}\) even for several million constraints, more than \(10{\times }\) shorter than prior SNARGs with similar features.