Authcoin: Validation and Authentication in Decentralized Networks
  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. 
Benjamin Leiding, Clemens H. Cap, Thomas Mundt, Samaneh Rashidibajgan
cs.CR