> > Returning info that explains why a server believes that the returned > data supports validation is an interesting notion. The first example > of that I saw was in work performed by colleagues here at BBN, on a > project calls IOS, in the early 90s, where servers did that. But, I > think this is still an R&D topic for now, not yet ready for > standardization.
Isn't part of this 'interesting notion' the cert chain itself. The certificate chain return by a DPV server is the chain that has been used to validate it, and the server believes that this chain is valid.
If the service is implemented using some relaying, such that a server becomes a client of someone else, what research problem is there that the intermediate server/client wants to provide the results? If for the initial client the result of the validation becomes something that can be stored somewhere, e.g. similar to an OCSP response stored in the SMIME/ETSI signature format stuff, then essentially this client becomes an intermediate server for another verifier of the enhanced signature.