Many open standards can support profile hydration:
- Ariadne
 - Map an email identifier to supported verified accounts.
 - The IndieWeb
 - Map a webpage with 
h-cardto any account. This can pair with other forms of authentication, such as RelMeAuth. - WebFinger
 - Map an email-like identifier (an 
acct:URI) to a list of links. - vCard
 - Mpload a vCard containing profile information, possibly with “share contact”.
 
I think h-card-based hydration is the best place to start. We can later add support for more options:
- Keyoxide profiles already contain 
h-cardmicroformats, so we get that for free. h-cardmicroformats can haveu-keyproperties, potentially triggering an Ariadne-based verification of accounts enumerated by theh-card.h-cardcan map to vCard4
Depending on how keyoxide-web issue 141 goes, WebFinger could also indirectly give Keyoxide support.