If you are looking for change visibility of dialog property based on user permissions / user cred, you can use renderconditions.
Create rendercondition like /libs/granite/ui/components/coral/foundation/renderconditions/privilege and use it on the dialog field like /libs/dam/gui/content/assets/annotate/jcr:content/actions/moveasset/granite:rendercondition.
If you want to get the user details in the dialog field, you should use jackrabit Usermanager API
Thanks for writing. I need to the the user who is updating the component in dialog listener (Touch UI). I want to store the user id/name of author who is updating the specific textarea(only) of a component. Assume a component has 5 fields in dialog, AEM stores the lastModifiedBy if any of those fields updated. I want to store the user name only when one(specific filed, say text area) of those five fields got updated.