Tag Archives: hash

Not even God forgives passwords in clear text

I think this comic from CommitStrip says it all:
CommitStrip clear text passwords

Passwords stored in clear text are half of the recipe to scary headlines such as “thousands of accounts published online by hackers”. To complete the recipe just add a single SQL injection or a good path traversal/LFI mix.

Mature and trained developers rarely make such mistake, why? Because they had training and understand the consequences. The problem is the others, which need to be self-taught.

So let me be very clear:

  • you don’t need passwords in clear text to compare against the ones from login
  • you can compare representations of them, lets say an hash
  • never store or log passwords

Regarding the storing itself, there are way too many options [1]. I will recommend just one, which is adequate for most situations (if you feel this does not fits you, please contact the nearest security guy, or leave a comment):

function store(password)
    salt = secureRandom(32bits)
    hash = pbkdf2(salt, password, 10000)


function validate(user, password)
    salt,hash = getUserFromDB(user).split(;)
    login_hash = pbkdf2(salt, password, 10000)

    if (login_hash XOR hash == 0 )
        return true
        return false

I won’t explain these in detail, but the basic idea is to store an hash of the password plus a salt. No, it is not easy to find out the password given an hash + salt. No, it won’t slow down your application. Yes, you will be much, much safer.

[1] https://www.owasp.org/index.php/Password_Storage_Cheat_Sheet