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9,005 results · page 297 of 376
Chris Berg
No abstract is available for this record.
Weijin Wang, Jingbin Liu, Yu Qin, Dengguo Feng
No abstract is available for this record.
Aggelos Kiayias, Annabell Kuldmaa, Helger Lipmaa, Janno Siim · 5 authors
No abstract is available for this record.
Juan A. Garay, Aggelos Kiayias, Nikos Leonardos, Giorgos Panagiotakos
No abstract is available for this record.
Zvika Brakerski, Vadim Lyubashevsky, Vinod Vaikuntanathan, Daniel Wichs
No abstract is available for this record.
Wilson Abel Alberto Torres, Ron Steinfeld, Amin Sakzad, Joseph K. Liu · 8 authors
No abstract is available for this record.
Bernardo David, Rafael Dowsley, Mario Larangeira
No abstract is available for this record.
Charanjit S. Jutla, Miyako Ohkubo, Arnab Roy
No abstract is available for this record.
Kanika Gupta, S. Sharmila Deva Selvi, C. Pandu Rangan, Shubham Sopan Dighe
No abstract is available for this record.
Fuyuki Kitagawa, Keisuke Tanaka
We propose a framework for achieving a public-key encryption (PKE) scheme that satisfies key dependent message security against chosen ciphertext attacks (KDM-CCA security) based on projective hash function. Our framework can be instantiated under the decisional diffie-hellman (DDH), quadratic residuosity (QR), and decisional composite residuosity (DCR) assumptions. The constructed schemes are KDM-CCA secure with respect to affine functions and compatible with the amplification method shown by Applebaum (EUROCRYPT 2011). Thus, they lead to PKE schemes satisfying KDM-CCA security for all functions computable by a-priori bounded size circuits. They are the first PKE schemes satisfying such a security notion in the standard model using neither non-interactive zero knowledge proof nor bilinear pairing. The above framework based on projective hash function captures only KDM-CCA security in the single user setting. However, we can prove the KDM-CCA security in the multi user setting of our concrete instantiations by using their algebraic structures explicitly. Especially, we prove that our DDH based scheme satisfies KDM-CCA security in the multi user setting with the same parameter setting as in the single user setting.
Wenshi Wang
No abstract is available for this record.
Yusuke Sakai, Shuichi Katsumata, Nuttapong Attrapadung, Goichiro Hanaoka
No abstract is available for this record.
Zuoxia Yu, Man Ho Au, Rupeng Yang, Junzuo Lai · 5 authors
No abstract is available for this record.
Charanjit S. Jutla, Arnab Roy
No abstract is available for this record.
Masayuki Abe, Charanjit S. Jutla, Miyako Ohkubo, Arnab Roy
We construct the first (almost) tightly-secure unbounded-simulation-sound quasi-adaptive non-interactive zero-knowledge arguments (USS-QA-NIZK) for linear-subspace languages with compact (number of group elements independent of the security parameter) common reference string (CRS) and compact proofs under standard assumptions in bilinear-pairings groups. In particular, under the SXDH assumption, the USS-QA-NIZK proof size is only seventeen group elements with a factor \(O(\log {Q})\) loss in security reduction to SXDH. The USS-QA-NIZK primitive has many applications, including structure-preserving signatures (SPS), CCA2-secure publicly-verifiable public-key encryption (PKE), which in turn have applications to CCA-anonymous group signatures, blind signatures and unbounded simulation-sound Groth-Sahai NIZK proofs. We show that the almost tight security of our USS-QA-NIZK translates into constructions of all of the above applications with (almost) tight-security to standard assumptions such as SXDH and, more generally, \(\mathcal{D}_k\)-MDDH. Thus, we get the first publicly-verifiable (almost) tightly-secure multi-user/multi-challenge CCA2-secure PKE with practical efficiency under standard bilinear assumptions. Our (almost) tight SPS construction is also improved in the signature size over previously known constructions.
Keisuke Hara, Fuyuki Kitagawa, Takahiro Matsuda, Goichiro Hanaoka · 5 authors
No abstract is available for this record.
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.
Chao Lin, Debiao He, Xinyi Huang, Muhammad Khurram Khan · 5 authors
Blockchain can potentially be deployed in a wide range of applications due to its capability to ensure decentralization, transparency, and immutability. In this paper, we design a cryptographic membership authentication scheme (i.e., authenticating graph data) to support blockchain-based identity management systems (BIMS). Such a system is designed to bind a digital identity object to its real-world entity. Specifically, we introduce a new transitively closed undirected graph authentication (TCUGA) scheme, which only needs to use node signatures (e.g., certificates for identifying nodes). The trapdoor hash function used in our scheme allows the signer to efficiently update the certificates without the need to re-sign the nodes. In other words, our scheme is efficient even though the graph dynamically adds or deletes vertices and edges. Moreover, our proposal can efficiently provide a proof when the edge between two vertices does not exist, thus solving the existing intractability issue in transitive signature (the main tool for authenticating graph data). Finally, we prove the security of our proposed TCUGA in the standard model and evaluate its performance to show its feasibility for BIMS.
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.
T-H. Hubert Chan, Rafael Pass, Elaine Shi
No abstract is available for this record.