Public key signatures for a distributed Facebook, LinkedIn & news service

Is a classification system of relationships all that is needed to usher in distributed implementations of the functionality of Facebook, LinkedIn and of news services?

Public key cryptography allows you to sign stuff in an efficient way: You sign it with your private key and enclose your public key. There it is, signed in your good name. But what does what you've signed mean? It must have a relationship to something else, and that relationship needs to be of a kind:

Lucy loves Ricky

That could be expressed as the private key of Lucy's signing a relationship "loves", including Ricky's public key (and her own public key). Now, anyone who got across this statement could verify it as being correctly signed. There is no need for a central database of the statement "Lucy loves Ricky", but there is a need for a way to make sure the public keys do indeed belong to Lucy and Ricky respectively.

This is where a web of trust comes in. As long as you have good access to a web of trust, the actual statements of relationships can be stored anywhere, redundantly, and be retrieved by a search engine. A blockchain can be used to order relationship statements in time, including revocations.

The vocabulary

One would ned to agree on a vocabulary of relation types such as:

• loves
• likes
• friends with
• worked for
• knows skill of X
• witnessed event X
• concludes conclusion X