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927 results · page 18 of 39
Nir Bitansky, Michael Kellner, Omri Shmueli
No abstract is available for this record.
Veronika Kuchta, Amin Sakzad, Ron Steinfeld, Joseph K. Liu
No abstract is available for this record.
Hanwen Feng, Qiang Tang
No abstract is available for this record.
Julia Hesse, Dennis Hofheinz, Lisa Kohl, Roman Langrehr
We investigate the quality of security reductions for non-interactive key exchange (NIKE) schemes. Unlike for many other cryptographic building blocks (like public-key encryption, signatures, or zero-knowledge proofs), all known NIKE security reductions to date are non-tight, i.e., lose a factor of at least the number of users in the system. In that sense, NIKE forms a particularly elusive target for tight security reductions. The main technical obstacle in achieving tightly secure NIKE schemes are adaptive corruptions. Hence, in this work, we explore security notions and schemes that lie between selective security and fully adaptive security. Concretely: We exhibit a tradeoff between key size and reduction loss. We show that a tighter reduction can be bought by larger public and secret NIKE keys. Concretely, we present a simple NIKE scheme with a reduction loss of O(N2log (ν) / ν2), and public and secret keys of O(ν) group elements, where N denotes the overall number of users in the system, and ν is a freely adjustable scheme parameter. Our scheme achieves full adaptive security even against multiple “test queries” (i.e., adversarial challenges), but requires keys of size O(N) to achieve (almost) tight security under the matrix Diffie-Hellman assumption. Still, already this simple scheme circumvents existing lower bounds. We show that this tradeoff is inherent. We contrast the security of our simple scheme with a lower bound for all NIKE schemes in which shared keys can be expressed as an “inner product in the exponent”. This result covers the original Diffie-Hellman NIKE scheme, as well as a large class of its variants, and in particular our simple scheme. Our lower bound gives a tradeoff between the “dimension” of any such scheme (which directly corresponds to key sizes in existing schemes), and the reduction quality. For ν= O(N), this shows our simple scheme and reduction optimal (up to a logarithmic factor). We exhibit a tradeoff between security and key size for tight reductions. We show that it is possible to circumvent the inherent tradeoff above by relaxing the desired security notion. Concretely, we consider the natural notion of semi-adaptive security, where the adversary has to commit to a single test query after seeing all public keys. As a feasibility result, we bring forward the first scheme that enjoys compact public keys and tight semi-adaptive security under the conjunction of the matrix Diffie-Hellman and learning with errors assumptions. We believe that our results shed a new light on the role of adaptivity in NIKE security, and also illustrate the special role of NIKE when it comes to tight security reductions.
Karim Baghery, Cyprien Delpech de Saint Guilhem, Emmanuela Orsini, Nigel P. Smart · 5 authors
This paper introduces M-Circuits, a program representation which generalizes arithmetic and binary circuits. This new representation is motivated by the way modern multi-party computation (MPC) systems based on linear secret sharing schemes actually operate. We then show how this representation also allows one to construct zero knowledge proof (ZKP) systems based on the MPC-in-the-head paradigm. The use of the M-Circuit program abstraction then allows for a number of program-specific optimizations to be applied generically. It also allows to separate complexity and security optimizations for program compilation from those for application protocols (MPC or ZKP).
Briag Dupont, Christian Franck, Johann Großschädl
No abstract is available for this record.
Yilei Chen, Alex Lombardi, Fermi Ma, Willy Quach
No abstract is available for this record.
Guillaume Kaim, Sébastien Canard, Adeline Roux-Langlois, Jacques Traoré
No abstract is available for this record.
François Garillot, Yashvanth Kondi, Payman Mohassel, Valeria Nikolaenko
No abstract is available for this record.
Yuyu Wang, Jiaxin Pan, Yu Chen
No abstract is available for this record.
Vijay Kumar Yadav, Rakesh Kumar Yadav, Brijesh Kumar Chaurasia, Shekhar Verma · 5 authors
No abstract is available for this record.
Ashrujit Ghoshal, Stefano Tessaro
No abstract is available for this record.
Teik Guan Tan, Jianying Zhou
No abstract is available for this record.
Amit Sahai, Brent Waters
We introduce a new technique, that we call punctured programs, to apply indistinguishability obfuscation towards cryptographic problems. We use this technique to carry out a systematic study of the applicability of indistinguishability obfuscation to a variety of cryptographic goals. Along the way, we resolve the 16-year-old open question of Deniable Encryption, posed by Canetti, Dwork, Naor, and Ostrovsky in 1997: In deniable encryption, a sender who is forced to reveal to an adversary both her message and the randomness she used for encrypting it should be able to convincingly provide “fake” randomness that can explain any alternative message that she would like to pretend that she sent. We resolve this question by giving the first construction of deniable encryption that does not require any pre-planning by the party that must later issue a denial. In addition, we show the generality of our punctured programs technique by also constructing a variety of core cryptographic objects from indistinguishability obfuscation and one-way functions (or close variants). In particular we obtain: public key encryption, short “hash-and-sign” selectively secure signatures, chosen-ciphertext secure public key encryption, non-interactive zero knowledge proofs (NIZKs), injective trapdoor functions, and oblivious transfer. These results suggest the possibility of indistinguishability obfuscation becoming a “central hub” for cryptography. Amit Sahai is supported for this research effort in part from NSF grants 1228984, 1136174, 1118096, 1065276, 0916574 and 0830803, a Xerox Faculty Research Award, a Google Faculty Research Award, an equipment grant from Intel, and an Okawa Foundation Research Grant. The views expressed are those of the author and do not reflect the official policy or position of the National Science Foundation, or the U.S. Government. Brent Waters is supported by NSF CNS-0915361 and CNS-0952692, CNS-1228599 DARPA through the U.S. Office of Naval Research under Contract N00014-11-1-0382, DARPA N11AP20006, Google Faculty Research award, the Alfred P. Sloan Fellowship, Microsoft Faculty Fellowship, and Packard Foundation Fellowship. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of Defense or the U.S. Government.
Behzad Abdolmaleki, Hamidreza Khoshakhlagh, Helger Lipmaa
No abstract is available for this record.
Olivier Blazy, Xavier Bultel, Pascal Lafourcade, Octavio Pérez Kempner
No abstract is available for this record.
Hongrui Cui, Kaiyi Zhang
No abstract is available for this record.
Christoph Dobraunig, Lorenzo Grassi, Anna Guinet, Daniël Kuijsters
Motivated by new applications such as secure Multi-Party Computation (MPC), Fully Homomorphic Encryption (FHE), and Zero-Knowledge proofs (ZK), the need for symmetric encryption schemes that minimize the number of field multiplications in their natural algorithmic description is apparent. This development has brought forward many dedicated symmetric encryption schemes that minimize the number of multiplications in \( \mathbb {F}_{2^n} \) or \( \mathbb {F}_{p} \), with p being prime. These novel schemes have lead to new cryptanalytic insights that have broken many of said schemes. Interestingly, to the best of our knowledge, all of the newly proposed schemes that minimize the number of multiplications use those multiplications exclusively in S-boxes based on a power mapping that is typically \(x^3\) or \(x^{-1}\). Furthermore, most of those schemes rely on complex and resource-intensive linear layers to achieve a low multiplication count. In this paper, we present Ciminion, an encryption scheme minimizing the number of field multiplications in large binary or prime fields, while using a very lightweight linear layer. In contrast to other schemes that aim to minimize field multiplications in \( \mathbb {F}_{2^n} \) or \( \mathbb {F}_{p} \), Ciminion relies on the Toffoli gate to improve the non-linear diffusion of the overall design. In addition, we have tailored the primitive for the use in a Farfalle-like construction in order to minimize the number of rounds of the used primitive, and hence, the number of field multiplications as far as possible.
Xiao Liang, Omkant Pandey
General-purpose zero-knowledge proofs for all \(\mathsf {NP} \) languages greatly simplify secure protocol design. However, they inherently require the code of the underlying relation. If the relation contains black-box calls to a cryptographic function, the code of that function must be known to use the ZK proof, even if both the relation and the proof require only black-box access to the function. Rosulek (Crypto’12) shows that non-trivial proofs for even simple statements, such as membership in the range of a one-way function, require non-black-box access.
Maanas Midha, Amit Kumar Gupta, Priya Mathur
No abstract is available for this record.
San Ling, Khoa Nguyen, Duong Hieu Phan, Khai Hanh Tang · 5 authors
No abstract is available for this record.
Javier Herranz, Ramiro Pinilla, Manuel Sánchez-Raya
In an electronic voting procedure, mixing networks are used to ensure anonymity of the casted votes. Each node of the network re-encrypts the input list of ciphertexts and randomly permutes it in a process named shuffle, and must prove (in zero-knowledge) that the process was applied honestly. To maintain security of such a process in a post-quantum scenario, new proofs are based on different mathematical assumptions, such as lattice-based problems. Nonetheless, the best lattice-based protocols to ensure verifiable shuffling have linear communication complexity on N, the number of shuffled ciphertexts.
Shuichi Katsumata
Many of the recent advanced lattice-based \(\varSigma \)-/public-coin honest verifier (HVZK) interactive protocols based on the techniques developed by Lyubashevsky (Asiacrypt’09, Eurocrypt’12) can be transformed into a non-interactive zero-knowledge (NIZK) proof in the random oracle model (ROM) using the Fiat-Shamir transform. Unfortunately, although they are known to be secure in the classical ROM, existing proof techniques are incapable of proving them secure in the quantum ROM (QROM). Alternatively, while we could instead rely on the Unruh transform (Eurocrypt’15), the resulting QROM secure NIZK will incur a large overhead compared to the underlying interactive protocol.
Seiya Nuta, Jacob C. N. Schuldt, Takashi Nishide
No abstract is available for this record.