1.20.x password.inc _password_generate_salt($count_log2)

Generates a random base 64-encoded salt prefixed with settings for the hash.

Proper use of salts may defeat a number of attacks, including:

  • The ability to try candidate passwords against multiple hashes at once.
  • The ability to use pre-hashed lists of candidate passwords.
  • The ability to determine whether two users have the same (or different) password without actually having to guess one of the passwords.


$count_log2: Integer that determines the number of iterations used in the hashing process. A larger value is more secure, but takes more time to complete.

Return value

A 12 character string containing the iteration count and a random salt.:


includes/password.inc, line 99
Secure password hashing functions for user authentication.


function _password_generate_salt($count_log2) {
  $output = '$S$';
  // Ensure that $count_log2 is within set bounds.
  $count_log2 = _password_enforce_log2_boundaries($count_log2);
  // We encode the final log2 iteration count in base 64.
  $itoa64 = _password_itoa64();
  $output .= $itoa64[$count_log2];
  // 6 bytes is the standard salt for a portable phpass hash.
  $output .= _password_base64_encode(backdrop_random_bytes(6), 6);
  return $output;