Password hash Security

Workzeug is a package for password hashing

>>> from werkzeug.security import generate_password_hash
>>> hash = generate_password_hash('foobar')
>>> hash
'pbkdf2:sha256:50000$vT9fkZM8$04dfa35c6476acf7e788a1b5b3c35e217c78dc04539d295f011f01f18cd2175f'

Verification process

>>> from werkzeug.security import check_password_hash
>>> check_password_hash(hash, 'foobar')
True
>>> check_password_hash(hash, 'barfoo')
False

multiple hash

Werkzeug generate_password_hash("same password") genereates different output each time when i run it multiple times

The password is salted, yes. The salt is added to the password before hashing, to ensure that the hash isn't useable in a rainbow table attack.

Because the salt is randomly generated each time you call the function, the resulting password hash is also different. The returned hash includes the generated salt so that can still correctly verify the password.

Demo:

>>> from werkzeug.security import generate_password_hash
>>> generate_password_hash('foobar')
'pbkdf2:sha1:1000$tYqN0VeL$2ee2568465fa30c1e6680196f8bb9eb0d2ca072d'
>>> generate_password_hash('foobar')
'pbkdf2:sha1:1000$XHj5nlLU$bb9a81bc54e7d6e11d9ab212cd143e768ea6225d'

These two strings differ; but contain enough information to verify the password because the generated salt is included in each:

# pbkdf2:sha1:1000$tYqN0VeL$2ee2568465fa30c1e6680196f8bb9eb0d2ca072d
  ^^^^^^^^^^^^^^^^   salt   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      algo info    ^^^^^^^^        actual hash of the password
  (PBKDF2 applied SHA1 1000 times)

Because the random salt is tYqN0VeL for one and XHj5nlLU, the resulting hash is also different.

The foobar password can still be verified against either hash:

>>> from werkzeug.security import check_password_hash
>>> check_password_hash('pbkdf2:sha1:1000$tYqN0VeL$2ee2568465fa30c1e6680196f8bb9eb0d2ca072d', 'foobar')
True
>>> check_password_hash('pbkdf2:sha1:1000$XHj5nlLU$bb9a81bc54e7d6e11d9ab212cd143e768ea6225d', 'foobar')
True 


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