gf_encrypt

add_filter("gform_save_field_value", "save_field_value", 10, 4);
function save_field_value ($value, $lead, $field, $form) {
    if (strpos(strtolower($form['title']), 'confidential') !== FALSE && strpos(strtolower($field['label']), 'program date') === FALSE) {
         switch ($field['type']) {
              case 'radio':
              case 'select':
              case 'checkbox':
              break;
              default:
                  $value = '%%enc%%' . custom_encrypt_func($value) . '%%end%%';
         }
    }
    return $value;
}

add_filter("gform_get_field_value", "get_field_value", 10, 3);
add_filter("gform_entry_field_value", "get_field_value", 10, 4);
function get_field_value ($value, $lead, $field, $form=NULL) {
    if (is_array($value)) {
        foreach ($value as &$val) {
            $val = _get_one_field_value($val);
        }
    } else {
        $value = _get_one_field_value($value);
    }
    return $value;
}

function _get_one_field_value ($value) {
    $value = preg_replace_callback(
        '/%%enc%%(.+?)%%end%%/',
        create_function(
            '$matches',
            'return custom_decrypt_func($matches[1]);'
        ),
        $value
    );
    return $value;
}