Password Storage Cheat Sheet

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Contents

DRAFT CHEAT SHEET - WORK IN PROGRESS

Introduction

This article is focused on providing guidance to storing a password in order to help prevent password theft. Too often passwords are stored as clear text. Thus the password can be read directly by the database’s administrator, super users or via data theft by SQL Injection. Database backup media is also vulnerable to password theft via password storage. It is recommended that you avoid storing the clear text password or an encrypted version of the password.

Password Storage Rules

Passwords are secrets. There is no reason to decrypt them under any circumstances. It is crucial that passwords are stored in a way that they can be *verified* but not *reversed* in any way, even by insiders. To accomplish this, store the salted hashed value of the password. Preferably use a different random salt for each password hash instead of a constant long salt.

  1. Use a modern hash
    1. SHA
    2. bcrypt
  2. Use a long cryptographically random salt
    1. Isolate the salt from the hash
  3. Iterate the hash

References

Cryptographic framework for password hashing is described in PKCS #5 v2.1: Password-Based Cryptography Standard. Specific secure password hashing algorithms exist such as bcrypt, scrypt. Implementations of secure password hashing exist for PHP (phpass), ASP.NET (ASP.NET 2.0 Security Practices), Java (OWASP Hashing Java).

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