We propose a new approach for a secure decentralized and censorless upgrade of existing cryptocurrencies to newly created tokens without interaction from any external information sources (oracles). The proposed scheme is based on burning of existing cryptocurrencies tokens and implemented via the multi-currency auction. The auction is carried out on the blockchain of the new token and implemented using a smart-contract that processes participants' bids of burnt tokens of other cryptocurrencies and supports a new token price discovery algorithm for each cryptocurrency with no oracles or any other trusted source of information. Contrary to traditional ways of getting the new asset, like centralized and decentralized exchanges, etc., our method requires no user registration (as well as no KYC – “know your customer” procedure that requires obligatory client identification) and provides a predicted supply level of the new asset for an adequate price within a model with economically rational participants. We provide the results of decentralized auction simulations implemented for several strategies of user behavior (based on bid prices with normal and log-normal distribution laws), both under the normal operation and in the presence of adversary who follows specific strategies.

Many blockchain applications require democratic on-chain decision-making. In this work, we propose a community-inclusive decentralised collaborative decision-making system with privacy assurance. Its key component is a two-stage voting scheme inspired by choice architecture. Our decision-making system is compatible with most existing blockchain infrastructures. In addition, it supports liquid democracy/delegative voting for better collaborative intelligence. Namely, stake holders can either vote directly on proposals or delegate their voting power to experts. When majority of voting committee members are honest, no one can derive voters’ voting preferences or delegations with non-negligible probability. To support concurrent multiple voting events, we design a distributed batch key generation protocol that can generate multiple keys simultaneously by voting committee members with amortised communication cost of$\mathcal {O}(n)$per key, where$n$is the number of participants. Besides, our system supports “evolving committee”, i.e., voting committee members can be changed during the voting period. We implemented a pilot system in Scala, benchmark results indicate that our system can support large number of participants with high efficiency.

Part of the design of many blockchains and cryptocurrencies includes a treasury, which periodically allocates collected funds to various projects that could be beneficial to their ecosystem. These projects are then voted on and selected by the users of the respective cryptocurrency. To better inform the users' choices, the proposals can be reviewed, in distributed fashion. Motivated by these intricacies, we study the problem of crowdsourcing reviews for different proposals, in parallel. During the reviewing phase, every reviewer can select the proposals to write reviews for, as well as the quality of each review. The quality levels follow certain very coarse community guidelines (since the review of the reviews has to be robust enough, even though it is also crowdsourced) and can have values such as 'excellent' or 'good'. Based on these scores and the distribution of reviews, every reviewer will receive some reward for their efforts. In this paper, we consider a simple and intuitive reward scheme and show that it always has pure Nash equilibria, under two different scenarios. In addition, we show that these equilibria guarantee constant factor approximations for two natural metrics: the total quality of all reviews, as well as the fraction of proposals that received at least one review, compared to the optimal outcome.

We introduce Zendoo, a construction for Bitcoin-like blockchain systems that allows the creation and communication with sidechains of different types without knowing their internal structure. We consider a parent-child relationship between the mainchain and sidechains, where sidechain nodes directly observe the mainchain while mainchain nodes only observe cryptographically authenticated certificates from sidechain maintainers. We use zk-SNARKs to construct a universal verifiable transfer mechanism that is used by sidechains.