title: password reset and encrypt-decrypt relation in php
body: <p>I use password in not only signIn but also encryption.
  And signIn password is crypted md5.
  If I lost / forget password. How can I decrypt my data?</p>
  
  <p>for example. user sign in with password = 1234.
  if signed in => decrypt data by using that password.</p>
  
  <p>I don't want to save my password in userdata for user privacy issue. 
  I want make user believe their data can only read by themselves.</p>
  
  <p>If user change password, how can I decrypt encrypted-data?
  Because password is a key for encrypt-decrypt. </p>
  
  <p>Thank.</p>