With respect to a special class of access structures based on connectivity of graphs, we start from a linear secret sharing scheme and turn it into a secret sharing scheme with perfect security and exponentially small error probability by randomizing the reconstruction algorithm through random walks on graphs. It reduces the polynomial work space to logarithmic. Then we build the corresponding statistical multiparty computation protocol by using the secret sharing scheme. The results of this paper also imply the inherent connections and influences among secret sharing, randomized algorithms, and secure multiparty computation.
With respect to a special class of access structures based on connectivity of graphs, we start from a linear secret sharing scheme and turn it into a secret sharing scheme with perfect security and exponentially small error probability by randomizing the reconstruction algorithm through random walks on graphs. It reduces the polynomial work space to logarithmic. Then we build the corresponding statistical multiparty computation protocol by using the secret sharing scheme. The results of this paper also imply the inherent connections and influences among secret sharing, randomized algorithms, and secure multiparty computation.
A multi-secret sharing scheme is the extension of a secret sharing scheme to the case in which there are many secrets need to be shared, and each secret may with different qualified subsets of participants. We study multi-secret sharing schemes based on random walks on graphs. Since many problems of secret sharing can be seen as having structure of the graphs. Different access structures corresponding to different walks for a graph with n vertices can be defined. So considering multi-secret sharing scheme based on random walks on graphs is meaningful. We prove that there exists multi-secret sharing schemes based on random walks on graphs by studying monotone span programs computing monotone Boolean function and secret sharing schemes realizing these classes of access structure.
We first study the problem of doing Verifiable Secret Sharing (VSS) information theoretically secure for a general access structure.We do it in the model where private channels between players and a broadcast channel is given, and where an active, adaptive adversary can corrupt any set of players not in the access structure.In particular, we consider the complexity of protocols for this problem, as a function of the access structure and the number of players.For all access structures where VSS is possible at all, we show that, up to a polynomial time black-box reduction, the complexity of adaptively secure VSS is the same as that of ordinary secret sharing (SS), where security is only required against a passive, static adversary.Previously, such a connection was only known for linear secret sharing and VSS schemes.We then show an impossibility result indicating that a similar equivalence does hot hold for Multiparty Computation (MPC): we show that even if protocols are given black-box access for free to an idealized secret sharing scheme secure for the access structure in question, it is not possible to handle all relevant access structures efficiently, not even if the adversary is passive and static.In other words, general MPC can only be black-box reduced efficiently to secret sharing if extra properties of the secret sharing scheme used (such as linearity) are assumed.
We show a general connection between various types of statistical zero-knowledge (SZK) proof systems and (unconditionally secure) secret sharing schemes. Viewed through the SZK lens, we obtain several new results on secret-sharing: Characterizations: We obtain an almost-characterization of access structures for which there are secret-sharing schemes with an ecient sharing algorithm (but not necessarily ecient reconstruction). In particular, we show that for every language L2 SZKL (the class of languages that have statistical zero knowledge proofs with log-space veriers and simulators), a (monotonized) access structure associated with L has such a secretsharing scheme. Conversely, we show that such secret-sharing schemes can only exist for languages in SZK. Constructions: We show new constructions of secret-sharing schemes with ecient sharing and reconstruction for access structures that are in P, but are not known to be in NC, namely Bounded-Degree Graph Isomorphism and constant-dimensional lattice problems. In particular, this gives us the rst combinatorial access structure that is conjectured to be outside NC but has an ecient secret-sharing scheme. Previous such constructions (Beimel and Ishai; CCC 2001) were algebraic and number-theoretic in nature. Limitations: We show that universally-ecie nt secret-sharing schemes, where the complexity of computing the shares is a polynomial independent of the complexity of deciding the access structure, cannot exist for all (monotone languages in) P, unless there is a polynomial q such that P DSPACE(q(n)).
Verifiable Secret Sharing (VSS) is a fundamental primitive used as a building block in many distributed cryptographic tasks, such as Secure Multiparty Computation (MPC) and Byzantine Agreement (BA). An important variant of VSS is Asynchronous VSS (AVSS) which is designed to work over asynchronous networks. AVSS is a two phase (Sharing, Reconstruction) protocol carried out among n parties in the presence of a computationally unbounded active adversary, who can corrupt up to t parties. We assume that every two parties in the network are directly connected by a pairwise secure channel. In this paper, we present a new statistical AVSS protocol with optimal 5 resilience; i.e. with n = 3t + 1. Our protocol privately communicates
We first study the problem of doing Verifiable Secret Sharing (VSS) information theoretically secure for a general access structure. We do it in the model where private channels between players and a broadcast channel is given, and where an active, adaptive adversary can corrupt any set of players not in the access structure. In particular, we consider the complexity of protocols for this problem, as a function of the access structure and the number of players. For all access structures where VSS is possible at all, we show that, up to a polynomial time black-box reduction, the complexity of adaptively secure VSS is the same as that of ordinary secret sharing (SS), where security is only required against a passive, static adversary. Previously, such a connection was only known for linear secret sharing and VSS schemes. We then show an impossibility result indicating that a similar equivalence does not hold for Multiparty Computation (MPC): we show that even if protocols are given blac...
Abstract. As an extension of multi-party computation (MPC), we propose the concept of secure parallel multi-party computation which is to securely compute multi-functions against an adversary with multistructures. Precisely, there are m functions f1,..., fm and m adversary structures A1,..., Am, where fi is required to be securely computed against an Ai-adversary. We give a general construction to build a parallel multi-party computation protocol from any linear multi-secret sharing scheme (LMSSS), provided that the access structures of the LMSSS allow MPC at all. When computing complicated functions, our protocol has more advantage in communication complexity than the “direct sum” method which actually executes a MPC protocol for each function. The paper also provides an efficient and generic construction to obtain from any LMSSS a multiplicative LMSSS for the same multi-access structure. 1