How to change Drupal user password programmatically?

We are going to deploy a Drupal site inside company's intranet. There is a requirement for user to reset password. We have a centralized password reset mechanism (for single sign on):

• user submits a password change request in system
• the request is sent to a password server
• the password server will reset the user's password in all systems with a new password
• the password server will send the new password to user's mobile phone via sms

Now we are going to add the Drupal site to all systems. Please suggest a way to change the Drupal's logon password by an external program (assume the system can run script on the Drupal host and edit Drupal MySQL database).

If you're using Drupal 6 then the password stored in the system is a simple md5 of the password. If you're using php scripts to trigger the password reset then use the http://php.net/manual/en/function.md5.php function.

Username and Password is stored in the users table. The md5 hash is stored in the pass column.