The excellent Keybase.io service provides a means to make cryptographic claims to prove ownership of certain types of information. e.g. DNS, Twitter, etc. These proofs are independently verified by each client by retrieving a proof statement from each service in a service dependant manner.
However Keybase does not provide a way to make arbitrary claims for services, accounts, keys, etc. that are not officially supported. The ability to make such arbitrary claims, perhaps in the form of unverified key:value pairs which are