Communication-Efficient Proactive Secret Sharing for Dynamic Groups with Dishonest Majorities

In standard Secret Sharing (SS), a dealer shares a secret $s$ among $n$ parties such that an adversary corrupting no more than $t$ parties does not learn $s$, while any $t+1$ parties can efficiently recover $s$. Proactive Secret Sharing (PSS) retains confidentiality of $s$ even when a mobile adversary corrupts all parties over the lifetime of the secret, but no more than a threshold $t$ in each epoch (called a refresh period). Withstanding such adversaries has become of increasing importance with the emergence of settings where private keys are secret shared and used to sign cryptocurrency transactions, among other applications. Feasibility of single-secret PSS for static groups with dishonest majorities was demonstrated but with a protocol that requires inefficient communication of $O(n^4)$. In this work, we improve over prior work in three directions: batching without incurring a linear loss in corruption threshold, communication efficiency, and handling dynamic groups. While each of properties we improve upon appeared independently in the context of PSS and in other previous work, handling them simultaneously (and efficiently) in a single scheme faces non-trivial challenges. Some PSS protocols can handle batching of $\ell \sim n$ secrets, but all of them are for the honest majority setting. Techniques typically used to accomplish such batching decrease the tolerated corruption threshold bound by a linear factor in $\ell$, effectively limiting the number of elements that can be batched with dishonest majority. We solve this problem by reducing the threshold decrease to $\sqrt{\ell}$ instead, allowing us to deal with the dishonest majority setting when $\ell \sim n$. This is accomplished based on new bivariate-polynomials-based techniques for sharing, and refreshing and recovering of shares, that allow batching of up to $n-2$ secrets in our PSS. To tackle the efficiency bottleneck the constructed PSS protocol requires only $O(n^3/\ell)$ communication for $\ell$ secrets, i.e., an amortized communication complexity of $O(n^2)$ when the maximum batch size is used. To handle dynamic groups we develop three new sub-protocols to deal with parties joining and leaving the group

Fully abstract trace semantics of low-level isolation mechanisms

Many software systems adopt isolation mechanisms of modern processors as software security building blocks. Reasoning about these building blocks means reasoning about elaborate assembly code, which can be very complex due to the loose structure of the code. A way to overcome this complexity is giving the code a more structured semantics. This paper presents one such semantics, namely a fully abstract trace semantics, for an assembly language enhanced with protection mechanisms of modern processors. The trace semantics represents the behaviour of protected assembly code with simple abstractions, unburdened by low-level details, at the maximum degree of precision. Additionally, it captures the capabilities of attackers to protected software and simplifies providing a secure compiler targeting that language.status: publishe

Attacking Websites During Crises: Analysis and Solutions‬

Achieving key agreement in wireless sensor networks (WSN) is a very hard problem. Many key agreement schemes come with a shortage of considering sensor addition, revocation, and also rekeying. This paper proposes a key distribution protocol based on the public key cryptography, RSA, and DHECC. The proposed protocol does not trust individual sensors, and partially trust the Gateway. Our protocol establishes pair-wise keys between nodes according to a specific routing algorithm after deployment, instead of loading full pair-wise keys into each node. So each node doesn't have to share a key with all neighbors except those involved in the routing path with it, which is the key role of increasing the resiliency, against node capturing, and also the storage efficiency. The proposed scheme comes to circumvent the shortage of providing the rekeying property of nodes and also nodes addition and revocation, comes with previous algorithms. We evaluate our algorithm from the WSN security view point

Application of selective solid-phase extraction using a new core-shell-shell magnetic ion-imprinted polymer for the analysis of ultra-trace mercury in serum of gallstone patients

A new ultrasonically assisted spectrophotometric method was developed using stabilized ion polymer on a modified nano-absorbent as a core- shell-shell absorbent (Fe3O4@SiO2@TiO2–IIP). It has the advantages of further stabilizing the polymer and consequently and much higher efficiency than its conventional adsorbents. The prepared sorbent was characterized and Its parameters were investigated by a Box–Behnken design. The linear dynamic range and limit of detection were 0.20–28.00 µg L−1 and 0.05 µg L−1 respectively. In selectivity study, it was founded that imprinting causes increased affinity of the prepared IIP toward Hg2+ ion. The proposed IIP is considered to be promising and selective sorbent for solid-phase extraction and preconcentration of Hg2+ ion in sera of different types of gallstone patients. © 2019 Taylor & Francis

Semiorthogonal Decompositions on Enriques Surfaces and Derived Torelli Theorem

We show that the general Enriques surface can be recovered from the Kuznetsov component of its bounded derived category of coherent sheaves.Comment: Withdrawn due to serious concern about the correctness of one of the results in our bibliography which was a key part in our proo