List all machine name values for permissions in drupal 7

// Render permission overview:
$options = array();
foreach (module_list(FALSE, FALSE, TRUE) as $module) {
  if ($permissions = module_invoke($module, 'permission')) {
    // List only the modules that have permissions.
    dsm($module);
    dsm($permissions);
  }
}

you can also use Devel module and Enable "Display machine names of permissions and modules" option and will have it on hover at permission page.