code: public boolean clearEncryptionKeyData() {
          try {
              SharedPreferences.Editor editor = this.prefs.edit();
              editor.remove(preferenceKey);
              editor.commit();
          } catch (Exception e) {
              LOGGER.log(Level.SEVERE, e.getLocalizedMessage(), e);
              return false;
          }
          return true;
      }
docs: Remove from the {@link SharedPreferences} a {@link KeyData} associated to the same
  identifier used to
  create this storage.
  <p/>
  It will succeed if the data is deleted or if there is no data at all.
  
  @return true (success) or false (fail)