Key Transparency is admittedly a prototype, Google said. It could provide significant relief for secure messaging systems suffering from complexity that has seriously impeded mass adoption. Google engineers said it has integrated concepts from Certificate Transparency and CONIKS to build Key Transparency. The lookup service can be used to find public keys associated with an account, along with a public audit log of any changes. Google intends this prototype release as an engagement with cryptographers that will generate input driving Key Transparency toward a standard, engineers said.
Source: https://threatpost.com/googles-key-transparency-simplifies-public-key-lookups/123073/