2PC-MPC: Emulating Two Party ECDSA in Large-Scale MPC

Motivated by the need for a massively decentralized network concurrently servicing many clients, we present novel low-overhead UC-secure, publicly verifiable, threshold ECDSA protocols with identifiable abort. For the first time, we show how to reduce the message complexity from O(n^2) to O(n) and the computational complexity from O(n) to practically O(1) (per party, where n is the number of parties). We require only a broadcast channel for communication. Therefore, we natively support use-cases like permissionless bridges and decentralized custody, where P2P channels between every pair of parties are infeasible. Consequently, the message complexity is reduced and the protocol is publicly verifiable. We enable all communication to be public (over a broadcast channel), by using a threshold additively homomorphic encryption scheme and novel zero-knowledge proofs. To further reduce the computation and communication overheads, our protocols employ novel batching and amortization techniques, which may be of independent interest. Our second main contribution is the introduction of the notion of a 2PC-MPC protocol - a two-party ECDSA protocol where the second party is fully emulated by a network of n parties. This notion assures that both the first party (the client) and (a threshold) of the network are required to participate in signing, while abstracting away the internal structure of the network. In particular, the communication and computation complexities of the client remain independent of the network properties (e.g. size). This allows ultimate decentralization in distributed custody use-cases, as recent growing interest in the industry demands. We report that our implementation completes the signing phase in 1.23 and 12.703 seconds, for 256 and 1024 parties, respectively

Assessing the capacity of ministries of health to use research in decision-making: conceptual framework and tool

Abstract Background The capacity to demand and use research is critical for governments if they are to develop policies that are informed by evidence. Existing tools designed to assess how government officials use evidence in decision-making have significant limitations for low- and middle-income countries (LMICs); they are rarely tested in LMICs and focus only on individual capacity. This paper introduces an instrument that was developed to assess Ministry of Health (MoH) capacity to demand and use research evidence for decision-making, which was tested for reliability and validity in eight LMICs (Bangladesh, Fiji, India, Lebanon, Moldova, Pakistan, South Africa, Zambia). Methods Instrument development was based on a new conceptual framework that addresses individual, organisational and systems capacities, and items were drawn from existing instruments and a literature review. After initial item development and pre-testing to address face validity and item phrasing, the instrument was reduced to 54 items for further validation and item reduction. In-country study teams interviewed a systematic sample of 203 MoH officials. Exploratory factor analysis was used in addition to standard reliability and validity measures to further assess the items. Results Thirty items divided between two factors representing organisational and individual capacity constructs were identified. South Africa and Zambia demonstrated the highest level of organisational capacity to use research, whereas Pakistan and Bangladesh were the lowest two. In contrast, individual capacity was highest in Pakistan, followed by South Africa, whereas Bangladesh and Lebanon were the lowest. Conclusion The framework and related instrument represent a new opportunity for MoHs to identify ways to understand and improve capacities to incorporate research evidence in decision-making, as well as to provide a basis for tracking change