AFAIK, one of the bigger problems with implementing PGP on a wider scale is the need to trust a keyserver to provide the correct open keys and update them when necessary. If so, can the database be decentralized via a blockchain so that no entity has absolute control over it? Key rotation can be implemented via additional blocks containing new keys signed by the previous ones. Proof-of-work also functions as a kind of CAPTCHA to solve potential spam issues. Since the rate at which new keys are added shouldn't be high, low transaction speed doesn't matter either. Would this kind of setup work and if not, why?