Python for Cryptography: Introduction to Hashlib and Passlib

Introduction
Prerequisites
Installing Required Libraries
Hashlib
- Hash Functions
- Generating Hashes
Passlib
- Password Hashing
- Verifying Passwords
Conclusion

Introduction

Cryptography plays a crucial role in securing sensitive information, and Python provides powerful libraries to assist in implementing cryptographic functions. In this tutorial, we will explore two widely used libraries for cryptography in Python: hashlib and passlib.

The hashlib library includes various hash functions that allow us to generate hash values for data, while the passlib library provides robust password hashing and verification mechanisms. By the end of this tutorial, you will be able to generate hashes and implement secure password storage using these libraries.

Prerequisites

To follow along with this tutorial, it is recommended to have a basic understanding of Python programming and the command line interface. Additionally, you should have Python and pip (Python’s package installer) installed on your machine.

Installing Required Libraries

Before we start, we need to install the necessary libraries. Open your command line interface and execute the following command to install the hashlib and passlib libraries: shell pip install hashlib passlib Once the installation is complete, we can begin exploring the capabilities of these libraries.

Hashlib

The hashlib library in Python provides a wide range of hash functions, such as MD5, SHA1, SHA256, and more. These functions generate a fixed-size hash value based on the input data.

Hash Functions

Let’s begin by understanding the available hash functions in hashlib. Here are some commonly used functions:

md5(): This function returns the MD5 hash object.
sha1(): This function returns the SHA1 hash object.
sha256(): This function returns the SHA256 hash object.
sha512(): This function returns the SHA512 hash object.
Note: The hashlib library also provides other hash functions such as SHA224, SHA384, and more.

Generating Hashes

To generate a hash using hashlib, follow these steps:

Import the hashlib module:
```
 import hashlib
```
Select the desired hash function and create a hash object:
```
 sha1_hash = hashlib.sha1()
```
Convert the input data to bytes and pass it to the update() method of the hash object:
```
 sha1_hash.update(b"Hello, World!")
```
Note: It is important to convert the input data to bytes, as the update() method expects a bytes-like object.
Retrieve the hash value using the hexdigest() method:
```
 hash_value = sha1_hash.hexdigest()
 print(hash_value)
```
Running this code will output the SHA1 hash value of the input data.

With these steps in mind, let’s create a function that generates hashes for different hash functions: ```python import hashlib

def generate_hash(hash_function, data):
    hash_object = hash_function()
    hash_object.update(data.encode())
    return hash_object.hexdigest()

data = "Sample data"
print("MD5 Hash:", generate_hash(hashlib.md5, data))
print("SHA1 Hash:", generate_hash(hashlib.sha1, data))
print("SHA256 Hash:", generate_hash(hashlib.sha256, data))
``` Now you can run the above code, and it will generate the hashes for the provided input data using different hash functions.

Passlib

The passlib library in Python simplifies implementing password hashing and verification. It provides a high-level interface that abstracts the complexities of secure password storage.

Password Hashing

To hash a password using passlib, follow these steps:

Import the necessary modules:
```
 from passlib.hash import sha256_crypt
```
Generate a hash by calling the hash method of the selected password hashing scheme:
```
 hashed_password = sha256_crypt.hash("mysecretpassword")
```
Print the hashed password:
```
 print(hashed_password)
```
Running the above code will output the hashed password generated using the SHA-256 algorithm.

Verifying Passwords

To verify a password using passlib, follow these steps:

Import the necessary modules:
```
 from passlib.hash import sha256_crypt
```

Verify the password by calling the verify method of the password hashing scheme:

 correct_password = "mysecretpassword"
 hashed_password = sha256_crypt.hash(correct_password)
	
 is_valid = sha256_crypt.verify(correct_password, hashed_password)
 if is_valid:
     print("Password is valid.")
 else:
     print("Password is invalid.")

Running this code will output “Password is valid” if the provided password matches the hashed password; otherwise, it will output “Password is invalid”.

Conclusion

In this tutorial, we explored the hashlib and passlib libraries in Python for cryptographic operations. We learned how to generate hashes using different hash functions provided by hashlib, and we also saw how to hash and verify passwords using passlib. These libraries provide essential tools for securing sensitive information in Python applications.

Make sure to practice and experiment with the examples provided to solidify your understanding. Cryptography is a complex field, and it is crucial to use these libraries correctly to maintain data security.

Published: 19 February 2020