Authcoin is an alternative approach to the commonly used public key infrastructures such as central authorities and the PGP web of trust. It combines a challenge response-based validation and authentication process for domains, certificates, email accounts and public keys with the advantages of a block chain-based storage system. As a result, Authcoin does not suffer from the downsides of existing solutions and is much more resilient to sybil attacks.
@article{arxiv.1609.04955,
title = {Authcoin: Validation and Authentication in Decentralized Networks},
author = {Benjamin Leiding and Clemens H. Cap and Thomas Mundt and Samaneh Rashidibajgan},
journal= {arXiv preprint arXiv:1609.04955},
year = {2016}
}