No abstract

No abstract

No abstract

Mining for Bitcoins is a high-risk high-reward activity. Miners, seeking to reduce their variance and earn steadier rewards, collaborate in so-called pooling strategies where they jointly mine for Bitcoins. Whenever some pool participant is successful, the earned rewards are appropriately split among all pool participants. Currently a dozen of different pooling strategies (i.e., methods for distributing the rewards) are in use for Bitcoin mining.We here propose a formal model of utility and social welfare for Bitcoin mining (and analogous mining systems) based on the theory of discounted expected utility, and next study pooling strategies that maximize the social welfare of miners. Our main result shows that one of the pooling strategies actually employed in practice-the so-called geometric pay pool -achieves the optimal steady-state utility for miners when its parameters are set appropriately.Our results apply not only to Bitcoin mining pools, but any other form of pooled mining or crowdsourcing computations where the participants engage in repeated random trials towards a common goal, and where "partial" solutions can be efficiently verified.

Abstract.Is it possible to prove that two DNA-fingerprints match, or that they do not match, without revealing any further information about the fingerprints? Is it possible to prove that two objects have the same design without revealing the design itself? In the digital domain, zero-knowledge is an established concept where a prover convinces a verifier of a statement without revealing any information beyond the statement's validity. However, zero-knowledge is not as well-developed in the context of problems that are inherently physical. In this paper, we are interested in protocols that prove physical properties of physical objects without revealing further information. The literature lacks a unified formal framework for designing and analyzing such protocols. We suggest the first paradigm for formally defining, modeling, and analyzing physical zero-knowledge (PhysicalZK) protocols, using the Universal Composability framework. We also demonstrate applications of physical zero-knowledge to DNA profiling and neutron radiography. Finally, we explore public observation proofs, an analog of public-coin proofs in the context of PhysicalZK.