  The Blockchain and the programs running on it, called Smart Contracts, are
more and more applied in all fields requiring trust and strong certifications.
In this work we compare public and permissioned blockchains for industrial
applications. We propose a complete, original solution based on Ethereum to
implement a decentralized application. This solution is characterized by a set
of validator nodes running the blockchain using Proof-of-Authority consensus,
and including an Explorer enabling users to check blockchain state, and the
source code of the Smart Contracts running on it. From time to time, the hash
digest of the last mined block is written into a public blockchain to guarantee
immutability. The right to send transactions is granted by validator nodes to
users by endowing them with the local Ethers mined. Overall, the proposed
approach has the same transparency and immutability of a public blockchain,
without its drawbacks.
