What is Drupal's default password encryption method?

Drupal 8 and Drupal 7 use SHA512 by default with a salt. They run the hash through PHP's hash function numerous times to increase the computation cost of generating a password's final hash (a security technique called stretching).

With Drupal 8, the implementation is object oriented. There is a PasswordInterface which defines a hash method. The default implementation of that interface is in the PhpassHashedPassword class. That class' hash method calls the crypt method passing in SHA512 as the hashing algorithm, a password, and a generated salt. The class' crypt method is nearly the same as Drupal 7's _password_crypt() method.

With Drupal 7, the implementation is split into a couple global functions: user_hash_password() and _password_crypt().

Drupal 6 uses MD5 without a salt. The relevant function is user_save().

Here is an example hash from Drupal 7:

• "pass" : "$S$Dxl65W9p07LfQU7jvy5CnsyDpMoLujiAgzy123khcg1OJi/P9pKS"

• The characters 0-2 are the type ( $S$ is Drupal 7 )

• The character 3 is the number of log2 rounds (X) based on the position of the char in this list: './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz' So in our example 'D' would map to 15
• The characters 4-11 are the SALT
• The rest is a SHA512 hash using 2^X rounds.

• The binary result is then converted to a string using base64.

  $count = 1 << $count_log2;
  $hash = hash($algo, $salt . $password, TRUE);
  do { $hash = hash($algo, $hash . $password, TRUE);
  } while (--$count);

The whole process can be found in: mydrupalsite\includes\password.inc

It can be checked inside www\includes\password.inc

function user_check_password($password, $account) {
  if (substr($account->pass, 0, 2) == 'U$') {
    // This may be an updated password from user_update_7000(). Such hashes
    // have 'U' added as the first character and need an extra md5().
    $stored_hash = substr($account->pass, 1);
    $password = md5($password);
  }
  else {
    $stored_hash = $account->pass;
  }

  $type = substr($stored_hash, 0, 3);
  switch ($type) {
    case '$S$':
      // A normal Drupal 7 password using sha512.
      $hash = _password_crypt('sha512', $password, $stored_hash);
      break;
    case '$H$':
      // phpBB3 uses "$H$" for the same thing as "$P$".
    case '$P$':
      // A phpass password generated using md5.  This is an
      // imported password or from an earlier Drupal version.
      $hash = _password_crypt('md5', $password, $stored_hash);
      break;
    default:
      return FALSE;
  }
  return ($hash && $stored_hash == $hash);
}

Its been clearly written that "// A normal Drupal 7 password using sha512."