Multilevel Threshold Secret and Function Sharing based on the Chinese Remainder Theorem

A recent work of Harn and Fuyou presents the first multilevel (disjunctive) threshold secret sharing scheme based on the Chinese Remainder Theorem. In this work, we first show that the proposed method is not secure and also fails to work with a certain natural setting of the threshold values on compartments. We then propose a secure scheme that works for all threshold settings. In this scheme, we employ a refined version of Asmuth-Bloom secret sharing with a special and generic Asmuth-Bloom sequence called the {\it anchor sequence}. Based on this idea, we also propose the first multilevel conjunctive threshold secret sharing scheme based on the Chinese Remainder Theorem. Lastly, we discuss how the proposed schemes can be used for multilevel threshold function sharing by employing it in a threshold RSA cryptosystem as an example

Web usability guidelines for smartphones : a synergic approach

The mobile phones that we carry with us all the time have started becoming increasingly sophisticated and consequently are referred to as “Smartphones”. Smartphones today are extremely powerful and, in addition to making phone calls, are capable of performing a variety of other functions. One very important function is the ability to access the Internet for a wide number of purposes. An obstacle that these users face is that access to the Internet is through a tiny interface, which is in sharp contrast to the typically large, flat-screen monitor. Unfortunately, many websites are neither designed for nor suitable to be accessed from these small devices. With relatively little effort, however, the developers of the websites can make the web interfaces more appropriate for Smartphones and hence accessible to a much larger audience. In this paper, we focus on “web usability”, a term essentially concerned with the ease of accessing and entering information on websites. We compile and synergize several different guidelines with the intent of increasing the web usability of Smartphones

On Hierarchical Threshold Secret Sharing

Recently, two novel schemes have been proposed for hierarchical threshold secret sharing, one based on Birkoff interpolation and another based on bivariate Lagrange interpolation. In this short paper, we propose a much simpler solution for this problem

Nested multipartite secret sharing

Quite recently, Tassa introduced an ideal and perfect secret sharing scheme realizing conjunctive hierarchical threshold access structures motivated by the problem of sharing a private key among three employees of a bank, at least one of whom must be a department manager, for the purpose of signing an electronic funds transfer. We ask the natural question concerning “What if there are two branches of banks that are needed to be involved in the signing process?” In such a case, one might encounter the presence of two distinct hierarchies involved in the same access structure. In this paper, being motivated by such a sample scenario, we describe a new generalization, what we name nested multipartite access structures, which may involve the well-known compartmented or hierarchical access structures as substructures. The corresponding generic scheme we describe employs multivariate interpolation and is ideal, linear and perfect with probability 1 - O(q -1 ) on a finite field F q . We describe the scheme in particular for the trivariate case as an example. Such an approach is hopefully useful not only for the initial motivating example, but also for a variety of interesting scenarios. In particular, we propose a non-nested generalization for the conventional compartmented access structures, which depicts a stronger way of controlling the additional t - (t 1 + ... + t m ) participants