73,881 research outputs found
Secret-Sharing from Robust Conditional Disclosure of Secrets
A secret-sharing scheme is a method by which a dealer, holding a secret string, distributes shares to parties such that only authorized subsets of parties can reconstruct the secret.
The collection of authorized subsets is called an access structure.
Secret-sharing schemes are an important tool in cryptography and they are used as a building box in many secure
protocols.
In the original constructions of secret-sharing schemes by Ito et al. [Globecom 1987], the share size of each party is (where is the number of parties in the access structure).
New constructions of secret-sharing schemes followed; however, the share size in these schemes remains basically the same.
Although much efforts have been devoted to this problem, no progress was made for more than 30 years.
Recently, in a breakthrough paper, Liu and Vaikuntanathan [STOC 2018] constructed a secret-sharing scheme for a general access structure with share size .
The construction is based on new protocols for conditional disclosure of secrets (CDS).
This was improved by Applebaum et al. [EUROCRYPT 2019] to .
In this work, we construct improved secret-sharing schemes for a general access structure with share size .
Our schemes are linear, that is, the shares are a linear function of the secret and some random elements from a finite field.
Previously, the best linear secret-sharing scheme had shares of size .
Most applications of secret-sharing require linearity. Our scheme is conceptually simpler than previous schemes, using a new reduction to two-party CDS protocols (previous schemes used a reduction to multi-party CDS protocols).
In a CDS protocol for a function , there are parties and a referee; each party holds a private input and a common secret, and sends one message to the referee (without seeing the other messages).
On one hand, if the function applied to the inputs returns , then it is required that the referee, which knows the inputs, can reconstruct the secret from the messages.
On the other hand, if the function applied to the inputs returns , then the referee should get no information on the secret from the messages. However, if the referee gets two messages from a party, corresponding to two different inputs (as happens in our reduction from secret-sharing to CDS), then the referee might be able to reconstruct the secret although it should not.
To overcome this problem, we define and construct -robust CDS protocols, where the referee cannot get any information on the secret when it gets messages for a set of zero-inputs of .
We show that if a function has a two-party CDS protocol with message size , then it has a two-party -robust CDS protocol with normalized message size .
Furthermore, we show that every function has a multi-linear -robust CDS protocol with normalized message size .
We use a variant of this protocol (with slightly larger than ) to construct our improved linear secret-sharing schemes.
Finally, we construct robust -party CDS protocols for
An Epitome of Multi Secret Sharing Schemes for General Access Structure
Secret sharing schemes are widely used now a days in various applications,
which need more security, trust and reliability. In secret sharing scheme, the
secret is divided among the participants and only authorized set of
participants can recover the secret by combining their shares. The authorized
set of participants are called access structure of the scheme. In Multi-Secret
Sharing Scheme (MSSS), k different secrets are distributed among the
participants, each one according to an access structure. Multi-secret sharing
schemes have been studied extensively by the cryptographic community. Number of
schemes are proposed for the threshold multi-secret sharing and multi-secret
sharing according to generalized access structure with various features. In
this survey we explore the important constructions of multi-secret sharing for
the generalized access structure with their merits and demerits. The features
like whether shares can be reused, participants can be enrolled or dis-enrolled
efficiently, whether shares have to modified in the renewal phase etc., are
considered for the evaluation
An ideal multi-secret sharing scheme based on minimal privileged coalitions
How to construct an ideal multi-secret sharing scheme for general access
structures is difficult. In this paper, we solve an open problem proposed by
Spiez et al.recently [Finite Fields and Their Application, 2011(17) 329-342],
namely to design an algorithm of privileged coalitions of any length if such
coalitions exist. Furthermore, in terms of privileged coalitions, we show that
most of the existing multi-secret sharing schemes based on Shamir threshold
secret sharing are not perfect by analyzing Yang et al.'s scheme and Pang et
al.'s scheme. Finally, based on the algorithm mentioned above, we devise an
ideal multi-secret sharing scheme for families of access structures, which
possesses more vivid authorized sets than that of the threshold scheme.Comment: 13page
Cryptographic techniques used to provide integrity of digital content in long-term storage
The main objective of the project was to obtain advanced mathematical methods to guarantee the verification that a required level of data integrity is maintained in long-term storage. The secondary objective was to provide methods for the evaluation of data loss and recovery. Additionally, we have provided the following initial constraints for the problem: a limitation of additional storage space, a minimal threshold for desired level of data integrity and a defined probability of a single-bit corruption.
With regard to the main objective, the study group focused on the exploration methods based on hash values. It has been indicated that in the case of tight constraints, suggested by PWPW, it is not possible to provide any method based only on the hash values. This observation stems from the fact that the high probability of bit corruption leads to unacceptably large number of broken hashes, which in turn stands in contradiction with the limitation for additional storage space.
However, having loosened the initial constraints to some extent, the study group has proposed two methods that use only the hash values. The first method, based on a simple scheme of data subdivision in disjoint subsets, has been provided as a benchmark for other methods discussed in this report. The second method ("hypercube" method), introduced as a type of the wider class of clever-subdivision methods, is built on the concept of rewriting data-stream into a n-dimensional hypercube and calculating hash values for some particular (overlapping) sections of the cube.
We have obtained interesting results by combining hash value methods with error-correction techniques. The proposed framework, based on the BCH codes, appears to have promising properties, hence further research in this field is strongly recommended.
As a part of the report we have also presented features of secret sharing methods for the benefit of novel distributed data-storage scenarios. We have provided an overview of some interesting aspects of secret sharing techniques and several examples of possible applications
An Effective Private Data storage and Retrieval System using Secret sharing scheme based on Secure Multi-party Computation
Privacy of the outsourced data is one of the major challenge.Insecurity of
the network environment and untrustworthiness of the service providers are
obstacles of making the database as a service.Collection and storage of
personally identifiable information is a major privacy concern.On-line public
databases and resources pose a significant risk to user privacy, since a
malicious database owner may monitor user queries and infer useful information
about the customer.The challenge in data privacy is to share data with
third-party and at the same time securing the valuable information from
unauthorized access and use by third party.A Private Information Retrieval(PIR)
scheme allows a user to query database while hiding the identity of the data
retrieved.The naive solution for confidentiality is to encrypt data before
outsourcing.Query execution,key management and statistical inference are major
challenges in this case.The proposed system suggests a mechanism for secure
storage and retrieval of private data using the secret sharing technique.The
idea is to develop a mechanism to store private information with a highly
available storage provider which could be accessed from anywhere using queries
while hiding the actual data values from the storage provider.The private
information retrieval system is implemented using Secure Multi-party
Computation(SMC) technique which is based on secret sharing. Multi-party
Computation enable parties to compute some joint function over their private
inputs.The query results are obtained by performing a secure computation on the
shares owned by the different servers.Comment: Data Science & Engineering (ICDSE), 2014 International Conference,
CUSA
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