1,582 research outputs found
A New PVSS Scheme with a Simple Encryption Function
A Publicly Verifiable Secret Sharing (PVSS) scheme allows anyone to verify
the validity of the shares computed and distributed by a dealer. The idea of
PVSS was introduced by Stadler in [18] where he presented a PVSS scheme based
on Discrete Logarithm. Later, several PVSS schemes were proposed. In [2],
Behnad and Eghlidos present an interesting PVSS scheme with explicit membership
and disputation processes. In this paper, we present a new PVSS having the
advantage of being simpler while offering the same features.Comment: In Proceedings SCSS 2012, arXiv:1307.8029. This PVSS scheme was
proposed to be used to provide a distributed Timestamping schem
Concurrently Non-Malleable Zero Knowledge in the Authenticated Public-Key Model
We consider a type of zero-knowledge protocols that are of interest for their
practical applications within networks like the Internet: efficient
zero-knowledge arguments of knowledge that remain secure against concurrent
man-in-the-middle attacks. In an effort to reduce the setup assumptions
required for efficient zero-knowledge arguments of knowledge that remain secure
against concurrent man-in-the-middle attacks, we consider a model, which we
call the Authenticated Public-Key (APK) model. The APK model seems to
significantly reduce the setup assumptions made by the CRS model (as no trusted
party or honest execution of a centralized algorithm are required), and can be
seen as a slightly stronger variation of the Bare Public-Key (BPK) model from
\cite{CGGM,MR}, and a weaker variation of the registered public-key model used
in \cite{BCNP}. We then define and study man-in-the-middle attacks in the APK
model. Our main result is a constant-round concurrent non-malleable
zero-knowledge argument of knowledge for any polynomial-time relation
(associated to a language in ), under the (minimal) assumption of
the existence of a one-way function family. Furthermore,We show time-efficient
instantiations of our protocol based on known number-theoretic assumptions. We
also note a negative result with respect to further reducing the setup
assumptions of our protocol to those in the (unauthenticated) BPK model, by
showing that concurrently non-malleable zero-knowledge arguments of knowledge
in the BPK model are only possible for trivial languages
Quantum Cryptography Beyond Quantum Key Distribution
Quantum cryptography is the art and science of exploiting quantum mechanical
effects in order to perform cryptographic tasks. While the most well-known
example of this discipline is quantum key distribution (QKD), there exist many
other applications such as quantum money, randomness generation, secure two-
and multi-party computation and delegated quantum computation. Quantum
cryptography also studies the limitations and challenges resulting from quantum
adversaries---including the impossibility of quantum bit commitment, the
difficulty of quantum rewinding and the definition of quantum security models
for classical primitives. In this review article, aimed primarily at
cryptographers unfamiliar with the quantum world, we survey the area of
theoretical quantum cryptography, with an emphasis on the constructions and
limitations beyond the realm of QKD.Comment: 45 pages, over 245 reference
Efficient UC Commitment Extension with Homomorphism for Free (and Applications)
Homomorphic universally composable (UC) commitments allow for the sender to reveal the result of additions and multiplications of values contained in commitments without revealing the values themselves while assuring the receiver of the correctness of such computation on committed values.
In this work, we construct essentially optimal additively homomorphic UC commitments from any (not necessarily UC or homomorphic) extractable commitment. We obtain amortized linear computational complexity in the length of the input messages and rate 1.
Next, we show how to extend our scheme to also obtain multiplicative homomorphism at the cost of asymptotic optimality but retaining low concrete complexity for practical parameters.
While the previously best constructions use UC oblivious transfer as the main building block, our constructions only require extractable commitments and PRGs, achieving better concrete efficiency and offering new insights into the sufficient conditions for obtaining homomorphic UC commitments.
Moreover, our techniques yield public coin protocols, which are compatible with the Fiat-Shamir heuristic.
These results come at the cost of realizing a restricted version of the homomorphic commitment functionality where the sender is allowed to perform any number of commitments and operations on committed messages but is only allowed to perform a single batch opening of a number of commitments.
Although this functionality seems restrictive, we show that it can be used as a building block for more efficient instantiations of recent protocols for secure multiparty computation and zero knowledge non-interactive arguments of knowledge
Efficient noninteractive certification of RSA moduli and beyond
In many applications, it is important to verify that an RSA public key (N; e) speci es a
permutation over the entire space ZN, in order to prevent attacks due to adversarially-generated
public keys. We design and implement a simple and e cient noninteractive zero-knowledge
protocol (in the random oracle model) for this task. Applications concerned about adversarial
key generation can just append our proof to the RSA public key without any other modi cations
to existing code or cryptographic libraries. Users need only perform a one-time veri cation of
the proof to ensure that raising to the power e is a permutation of the integers modulo N. For
typical parameter settings, the proof consists of nine integers modulo N; generating the proof
and verifying it both require about nine modular exponentiations.
We extend our results beyond RSA keys and also provide e cient noninteractive zero-
knowledge proofs for other properties of N, which can be used to certify that N is suitable
for the Paillier cryptosystem, is a product of two primes, or is a Blum integer. As compared to
the recent work of Auerbach and Poettering (PKC 2018), who provide two-message protocols for
similar languages, our protocols are more e cient and do not require interaction, which enables
a broader class of applications.https://eprint.iacr.org/2018/057First author draf
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