Is the user expected to recognize the public key fingerprint?
No, a PetName system remembers public key fingerprints for the user. The user can associate a personally chosen petname with a public key fingerprint. The PetName system will automatically recognize YURLs that use that public key fingerprint and display the corresponding petname. The user navigates a YURL web using only the personally chosen petnames, never even seeing the corresponding public key fingerprints.