Cryptographic Hashes and Message Digest in Python

A hash function is a one-way function that takes a string as a input and creates a fixed-length output (hash value of the corresponding input). Because it is a one-way function, it is very difficult to guess the original input.

This is why the passwords stored in a computer are hashed before storing so that even if a hacker gets access to the password database, he cannot guess the original password. In practice, we actually add a salt to the password to make it more difficult to bruteforce.

Here, in this post, we will find out how to generate the hash of a text using two popular python modules: hashlib and Crypto.

There are several hashing algorithms:

1. MD5
2. SHA1
3. SHA256
4. SHA512
5. HMAC

and some other variants of different output lengths.

Using hashlib module

We can use hashlib module in two ways to create object of a particular algorithm class.

The first way is pretty straightforward. Creating object by calling the algorithm class like this

obj1 = hashlib.md5()
obj2 = hashlib.sha256()

then we update data using the update() method

obj1.update("hello".encode())

or directly using the byte type data

obj1.update(b"hello")

finally we can generate the digest using the digest() or hexdigest() methods.

Here is an elaborated example that contains generated hash digests using different algorithms.

import hashlib

data = "This is a test"

hash_obj1 = hashlib.md5()
hash_obj1.update(data.encode())
print(f"Md5 Hash: {hash_obj1.hexdigest()}")

hash_obj2 = hashlib.sha1()
hash_obj2.update(data.encode())
print(f"SHA1 Hash: {hash_obj2.hexdigest()}")

hash_obj3 = hashlib.sha256()
hash_obj3.update(data.encode())
print(f"SHA256 Hash: {hash_obj3.hexdigest()}")

hash_obj4 = hashlib.sha512()
hash_obj4.update(data.encode())
print(f"SHA512 Hash: {hash_obj4.hexdigest()}")

Now, we can see the following output if run the program.

Md5 Hash: ce114e4501d2f4e2dcea3e17b546f339
SHA1 Hash: a54d88e06612d820bc3be72877c74f257b561b19
SHA256 Hash: c7be1ed902fb8dd4d48997c6452f5d7e509fbcdbe2808b16bcf4edce4c07d14e
SHA512 Hash: a028d4f74b602ba45eb0a93c9a4677240dcf281a1a9322f183bd32f0bed82ec72de9c3957b2f4c9a1ccf7ed14f85d73498df38017e703d47ebb9f0b3bf116f69

Another way to create object is using the new() method and passing the algorithm name as an argument.

obj1 = hashlib.new("md5")
obj2 = hashlib.new("sha256")

The elaborated example and output are as follows:

import hashlib

data = "This is a test"

hash_obj1 = hashlib.new("md5")
hash_obj1.update(data.encode())
print(f"Md5 Hash: {hash_obj1.hexdigest()}")

hash_obj2 = hashlib.new("sha1")
hash_obj2.update(data.encode())
print(f"SHA1 Hash: {hash_obj2.hexdigest()}")

hash_obj3 = hashlib.new("sha256")
hash_obj3.update(data.encode())
print(f"SHA256 Hash: {hash_obj3.hexdigest()}")

hash_obj4 = hashlib.new("sha512")
hash_obj4.update(data.encode())
print(f"SHA512 Hash: {hash_obj4.hexdigest()}")

We can make the whole code shorter by creating a function

import hashlib

def hashing(hash_type, data):
    hash_obj = hashlib.new(hash_type)
    hash_obj.update(data.encode())
    print(f"{hash_type} Hash: {hash_obj.hexdigest()}")

if __name__=="__main__":
    data = "This is a test"
    hash_types = ["md5", "sha1", "sha256", "sha512"]
    _ = [hashing(hash_type,data) for hash_type in hash_types]

If we run the program, we will find out the same outputs we have seen earlier.

Using pycrypto module

Another way to perform the same job is using the pycrypto module.

We can import all the necessary algorithm classes from Crypto.Hash.

An elaborated example is shown here:

from Crypto.Hash import HMAC, MD5, SHA as SHA1, SHA256

data = "This is a test"

hash_obj1 = MD5.new()
hash_obj1.update(data.encode())
print(f"Md5 Hash: {hash_obj1.hexdigest()}")

secret = "hello"
hash_obj2 = HMAC.new(secret.encode())
hash_obj2.update(data.encode())
print(f"HMAC Hash: {hash_obj2.hexdigest()}")

hash_obj3 = SHA1.new()
hash_obj3.update(data.encode())
print(f"SHA1 Hash: {hash_obj3.hexdigest()}")

hash_obj4 = SHA256.new()
hash_obj4.update(data.encode())
print(f"SHA256 Hash: {hash_obj4.hexdigest()}")

And the output is exactly the same.

Md5 Hash: ce114e4501d2f4e2dcea3e17b546f339
HMAC Hash: 842dbe36d5adb49ae838f7d146496852
SHA1 Hash: a54d88e06612d820bc3be72877c74f257b561b19
SHA256 Hash: c7be1ed902fb8dd4d48997c6452f5d7e509fbcdbe2808b16bcf4edce4c07d14e

In this post, we learnt a few basic examples of performing hash operations in python. Hope, that helps.

Until another post, cheers!!! :sunglasses:

References

1. hashlib - Secure hashes and message digests
2. Crypto.Hash package