Hashing User Passwords Using bcrypt in Python
Tags: security, python, programming, tutorial
Published: 2023-11-05 06:23:36

Web-based services and websites store hashed versions of your passwords, which means your actual password isn't visible or stored in their database instead a string of fixed-length characters is stored.

Hashing is a security technique used to secure your passwords or texts stored in databases. A hash function is used to generate a string of unique fixed-length characters from the provided password by the user.

Let's see how the hashing is done. In this article, you'll use the [bcrypt](https://pypi.org/project/bcrypt/) library to hash the user's password and then compare that hashed password to the actual password in Python. You'll also learn more about the bcrypt library.

## Installing bcrypt

Open your terminal window and run the following command to install the `bcrypt` library using ***pip***.

```bash
pip install bcrypt
```

Now that the `bcrypt` is installed in your system, the next step is to use it for hashing the user's password.

## Hash Password using bcrypt

In this section, you'll see the functions provided by the `bcrypt` library that will help you generate **salt** and **hash** values.

```python
import bcrypt

# Password to Hash
my_password = b'Sachinfromgeekpython'

# Generating Salt
salt = bcrypt.gensalt()

# Hashing Password
hash_password = bcrypt.hashpw(
    password=my_password,
    salt=salt
)

print(f"Actual Password: {my_password.decode('utf-8')}")
# Print Hashed Password
print(f"Hashed Password: {hash_password.decode('utf-8')}")
```

The above code imports the `bcrypt` library for hashing the password. A test password is provided in bytes and is stored inside the `my_password` variable.

The code uses the `gensalt()` function from the `bcrypt` library to generate the salt, a string of characters to enhance security.

> The salt is a random and unique string of characters combined with the password before hashing to provide additional security, it will always be unique, if two users have the same password, their hashed passwords will be different.

Then the actual password (`my_password`) and salt (`salt`) are passed to the `hashpw()` function from the `bcrypt` library to produce the hash value of the actual password.

Finally, the actual and hashed passwords are decoded and printed.

```bash
Actual Password: Sachinfromgeekpython
Hashed Password: $2b$12$RF6JLXecIE4qujuPgTwkC.GN2BsOmGf8Ji10LyquoBaHkHWUWgiAm
```

## Check Password using bcrypt

Now that you've hashed the password, the next step is to verify the actual password's hash value against the user-provided password.

```python
import bcrypt

# Password to Hash
my_password = b'Sachinfromgeekpython'

# Generating Salt
salt = bcrypt.gensalt()

# Hashing Password
hash_password = bcrypt.hashpw(
    password=my_password,
    salt=salt
)

# User-provided Password
user_password = b'Sachinfromgeekpython'

# Checking Password
check = bcrypt.checkpw(
    password=user_password,
    hashed_password=hash_password
)

# This will print True or False
print(check)

# Verifying the Password
if check:
    print("Welcome to GeekPython.")
else:
    print("Invalid Credential.")
```

The above code uses the `checkpw()` function from the `bcrypt` library to check the user-provided password against the hashed password. The hashed password (`hash_password`) and user-provided password (`user_password`) are passed inside the function and the result is stored inside the `check` variable.

Then the code prints the `check` variable to obtain the result. In the end, an `if-else` statement is used to verify the password.

```bash
True
Welcome to GeekPython.
```

`True` in the output above indicates that the hashed password matches the user-provided password, making the first condition true.

## Hash Password Using KDF (Key Derivation Function)

**KDF** (Key Derivation Function) is used to add additional security in password hashing. KDFs are used to derive keys from passwords for authentication purposes while including salt and the number of rounds.

```python
import bcrypt

password = b'Sachinfromgeekpython'
salt = bcrypt.gensalt()

# Using KDF from bcrypt Lib
key = bcrypt.kdf(
    password=password,
    salt=salt,
    desired_key_bytes=32,
    rounds=200
)

# Print Generated Key
print(f"Key: {key}")
```

The above code uses the `kdf()` function from the `bcrypt` library to derive a key from the password. The function is passed with four parameters:

* `password`: This parameter is set to the `password` variable which contains a byte string.
    
* `salt`: This parameter is set to the `salt` variable that contains a unique and fixed-length salt.
    
* `desired_key_bytes`: This parameter is set to `32` which is the desired length of the derived key we want. You can set it to your own desired length.
    
* `rounds`: This parameter is set to `200` which is the number of iterations to make the derivation of the key more computationally intense to increase security. The higher the rounds more the security but the more it uses resources and time.
    

Finally, the result stored in the `key` variable is printed.

```bash
Key: b'\xc4#VW\x9a\x16\xdbG?\x11\xa9\xf7\xbd\x88"7+zxo\xfe@\xce\xab\x89\xc3g\x1c\xec~\xbe\xf7'
```

## Verifying the Password with KDF

```python
import bcrypt

password = b'Sachinfromgeekpython'
salt = bcrypt.gensalt()

# Using KDF from bcrypt Lib
key = bcrypt.kdf(
    password=password,
    salt=salt,
    desired_key_bytes=32,
    rounds=200
)

# User-provided Password
user_password = b'Sachinfromgeekpython'

# Deriving Key from User-provided Password
user_key = bcrypt.kdf(
    password=user_password,
    salt=salt,
    desired_key_bytes=32,
    rounds=200
)

# Verifying the Password
if user_key == key:
    print("Welcome to GeekPython.")
else:
    print("Invalid Credential.")
```

The code derives the key from the user-provided password (`user_password`) and stores it inside the `user_key` variable.

Then the code verifies the derived keys from the user-provided password (`user_key`) and the actual password (`password`).

```bash
Welcome to GeekPython.
```

The output indicates that the key derived from the user-provided password matches the key derived from the actual password.

## Customizing Salt

The `gensalt()` function accepts two parameters: `rounds` and `prefix`, which allow you to customize the number of rounds of hashing to apply to the salt and prefix of the salt.

```python
import bcrypt

# Customize Salt
salt = bcrypt.gensalt(
    rounds=30,
    prefix=b'2a'
)

# Print Generated Salt
print(salt.decode('utf-8'))
```

The above code customizes the salt generation by passing the `rounds` parameter which is set to `30` and the `prefix` parameter which is set to `b'2a'` to the `gensalt()` function.

```bash
$2a$30$5uKaXaXVceqCjmKkPf2mnu
```

You can notice that in the beginning after `$`, above provided `2a` is prefixed, and just after that `30` indicates the number of rounds.

## Conclusion

Password hashing prevents exposing the user's actual password to the attackers. The hash function, which is simply a mathematical function is used to produce the hash value of the password.

In this article, you've learned to hash the user's password using the `bcrypt` library in Python and then check the produced hash value against the user-provided password. Additionally, you've seen the **KDF** (Key Derivation Function) that adds additional security for hashing.

---

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---

**That's all for now**

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