[dane-pgp]

It should be possible for each person to create multiple digital identities and have them linked using zero-knowledge proofs. If we can solve the messy problem of giving everyone (arbitrarily many uncensorable pseudonymous) IDs with their own key pairs, it should be relatively simple to layer on top of that all the functionality and privacy guarantees we would want from an ID system.

For example, once a reasonable digital ID system exists, we can start to build trust systems, such that your good reputation among one community can be used to bootstrap your reputation in a new community. Again, zero-knowledge proofs should be a viable mechanism for conveying trust relationships without having to reveal your social graph.

Some of this data would have to be stored off-chain, or only in encrypted form on-chain, but I don't think there are any practical limits of blockchain technology which prevent this.