Ethereum blockchain as a decentralized and autonomous key server: storing and extracting public keys through smart contracts

Ethereum is an open-source, public, blockchain-based distributed computing platform featuring smart contract functionality. It provides a decentralized Turing-complete virtual machine which can execute scripts using an international network of public nodes. The purpose of this thesis is to build a decentralized and autonomous key server using Ethereum smart contracts to store and retrieve information. We did an overall introduction of Bitcoin and Ethereum to provide a background of the study. We then analyzed the current problems of key discovery with traditional servers and web-of-trust. We designed, built and tested an application that can verify contact cards (email address, PGP public key, domain address, Facebook account), link them to an Ethereum address and store them on a public contract running on the Ethereum blockchain. Finally we made an analysis of the costs and limitations of such solution and proposed some future improvements. The results show that Ethereum is a good choice for storing public keys, thanks to the immutability and irreversibility of the blockchain.