Hashing Passwords


In this video lesson we discuss how to hash passwords in our Flask application.

First a shell demo:

>>> import hashlib
>>> pwd = 'LaunchCode'
>>> hashlib.sha256(str.encode(pwd)).hexdigest()

In the code example above we import the hashlib and create a sample password string. Then we call the hashlib.sha256() function on the password string after first converting it into a set of bytes using str.encode(). Then we get a string to store in the database, rather than an object, from the hash function using .hexdigest().

You can create two functions and store them in a reusable file named hashutils.py for your application's password hashing needs:

import hashlib

def make_pw_hash(password):
    return hashlib.sha256(str.encode(password)).hexdigest()

def check_pw_hash(password, hash):
    if make_pw_hash(password) == hash:
        return True

    return False

Next, after importing the above functions into main.py, you'll want to modify your User class so that you are storing password hashes instead of the password itself:

class User(db.Model):

    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(120), unique=True)
    pw_hash = db.Column(db.String(120))
    tasks = db.relationship('Task', backref='owner')

    def __init__(self, email, password):
        self.email = email
        self.pw_hash = make_pw_hash(password)

Now you'll need to update your database to get this to work since you've changed a model class (table) by dropping and re-creating the tables in a Python session.

And then you'll need to modify the login function so that it compares two hashes rather than two password strings:

if user and check_pw_hash(password, user.pw_hash):


View the final code from this lesson.