The 6 rules of password storage

This post is a quick writeup of the reasons behind password storage techniques, so I can refer to it instead of explaining a fresh every time. It is intended to be simple and easy so there is no excuse for not reading or understanding it.

  1. We must protect passwords not just for our own services security but for the security of all internet services. Users reuse passwords, in an ever connected internet, the value of a password is ever increasing.
  2. We must not store plain text passwords because databases have a habit of falling into the wrong hands.
  3. We must not use reversible encryption because keys are required all the time and have a habit of falling into the same wrong hands at the same time as the database.
  4. We must not simply hash the passwords. With a simple hash, every password that is the same hashes to the same value an attackers work to recover the passwords is therefore greatly reduced.
  5. We must not use a hash which has been intentionally built for speed such as Md5, Sha1 or Sha2. Dedicated hardware and GPU’s can calculate Billions to TRILLIONS of hashes per second. Password recovery by an attacker is inevitable.
  6. We must use a hashing algorithm designed for password storage such as PBKDF2, Bcrypt or Scrypt with appropriate cost parameters.


The information contained in this post was accurate at the time it was posted. If you are reading this more than 12-18 months after December 2015 you should double check with a more up to date source that the information is still valid before relying on it.