  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.
