Drupal private field
Use one theses modules :

User Field Privacy


  
  All the user fields should have an "alterable privacy" checkbox.
  If this checkbox is ticked, the user should be presented with an    additional checkbox for the privacy-enabled fields on user edit forms 
  to be able to make that fields' values private.
  If this second checkbox is ticked for a field of a user, only the    site administrators (members of roles with the "Access private
  fields" permission) and the user herself should be able to view that
  field's value.
  


CCK Private Fields


  This module allows users to mark administrator selected CCK fields as
  Public (visible to everyone), Hidden (visible to node author, hidden
  from everyone else) or Private (visible to node author and "friends";
  see requirements section below).


Field Permissions


  
  Enable field permissions on any entity, not just nodes.
  Role-based field permissions allowing different viewing patterned    based on what access the user has.
  Author-level permissions allow viewing and editing of fields based on    who the entity owner is.
  Permissions for each field are not enabled by default. Instead,    administrators can enable these permissions explicitly for the fields 
  where this feature is needed.