Python/hashes/sha256.py
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249 lines
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Python

# Author: M. Yathurshan
# Black Formatter: True
"""
Implementation of SHA256 Hash function in a Python class and provides utilities
to find hash of string or hash of text from a file.
Usage: python sha256.py --string "Hello World!!"
python sha256.py --file "hello_world.txt"
When run without any arguments,
it prints the hash of the string "Hello World!! Welcome to Cryptography"
References:
https://qvault.io/cryptography/how-sha-2-works-step-by-step-sha-256/
https://en.wikipedia.org/wiki/SHA-2
"""
import argparse
import struct
import unittest
class SHA256:
"""
Class to contain the entire pipeline for SHA1 Hashing Algorithm
>>> SHA256(b'Python').hash
'18885f27b5af9012df19e496460f9294d5ab76128824c6f993787004f6d9a7db'
>>> SHA256(b'hello world').hash
'b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9'
"""
def __init__(self, data: bytes) -> None:
self.data = data
# Initialize hash values
self.hashes = [
0x6A09E667,
0xBB67AE85,
0x3C6EF372,
0xA54FF53A,
0x510E527F,
0x9B05688C,
0x1F83D9AB,
0x5BE0CD19,
]
# Initialize round constants
self.round_constants = [
0x428A2F98,
0x71374491,
0xB5C0FBCF,
0xE9B5DBA5,
0x3956C25B,
0x59F111F1,
0x923F82A4,
0xAB1C5ED5,
0xD807AA98,
0x12835B01,
0x243185BE,
0x550C7DC3,
0x72BE5D74,
0x80DEB1FE,
0x9BDC06A7,
0xC19BF174,
0xE49B69C1,
0xEFBE4786,
0x0FC19DC6,
0x240CA1CC,
0x2DE92C6F,
0x4A7484AA,
0x5CB0A9DC,
0x76F988DA,
0x983E5152,
0xA831C66D,
0xB00327C8,
0xBF597FC7,
0xC6E00BF3,
0xD5A79147,
0x06CA6351,
0x14292967,
0x27B70A85,
0x2E1B2138,
0x4D2C6DFC,
0x53380D13,
0x650A7354,
0x766A0ABB,
0x81C2C92E,
0x92722C85,
0xA2BFE8A1,
0xA81A664B,
0xC24B8B70,
0xC76C51A3,
0xD192E819,
0xD6990624,
0xF40E3585,
0x106AA070,
0x19A4C116,
0x1E376C08,
0x2748774C,
0x34B0BCB5,
0x391C0CB3,
0x4ED8AA4A,
0x5B9CCA4F,
0x682E6FF3,
0x748F82EE,
0x78A5636F,
0x84C87814,
0x8CC70208,
0x90BEFFFA,
0xA4506CEB,
0xBEF9A3F7,
0xC67178F2,
]
self.preprocessed_data = self.preprocessing(self.data)
self.final_hash()
@staticmethod
def preprocessing(data: bytes) -> bytes:
padding = b"\x80" + (b"\x00" * (63 - (len(data) + 8) % 64))
big_endian_integer = struct.pack(">Q", (len(data) * 8))
return data + padding + big_endian_integer
def final_hash(self) -> None:
# Convert into blocks of 64 bytes
self.blocks = [
self.preprocessed_data[x : x + 64]
for x in range(0, len(self.preprocessed_data), 64)
]
for block in self.blocks:
# Convert the given block into a list of 4 byte integers
words = list(struct.unpack(">16L", block))
# add 48 0-ed integers
words += [0] * 48
a, b, c, d, e, f, g, h = self.hashes
for index in range(64):
if index > 15:
# modify the zero-ed indexes at the end of the array
s0 = (
self.ror(words[index - 15], 7)
^ self.ror(words[index - 15], 18)
^ (words[index - 15] >> 3)
)
s1 = (
self.ror(words[index - 2], 17)
^ self.ror(words[index - 2], 19)
^ (words[index - 2] >> 10)
)
words[index] = (
words[index - 16] + s0 + words[index - 7] + s1
) % 0x100000000
# Compression
s1 = self.ror(e, 6) ^ self.ror(e, 11) ^ self.ror(e, 25)
ch = (e & f) ^ ((~e & (0xFFFFFFFF)) & g)
temp1 = (
h + s1 + ch + self.round_constants[index] + words[index]
) % 0x100000000
s0 = self.ror(a, 2) ^ self.ror(a, 13) ^ self.ror(a, 22)
maj = (a & b) ^ (a & c) ^ (b & c)
temp2 = (s0 + maj) % 0x100000000
h, g, f, e, d, c, b, a = (
g,
f,
e,
((d + temp1) % 0x100000000),
c,
b,
a,
((temp1 + temp2) % 0x100000000),
)
mutated_hash_values = [a, b, c, d, e, f, g, h]
# Modify final values
self.hashes = [
((element + mutated_hash_values[index]) % 0x100000000)
for index, element in enumerate(self.hashes)
]
self.hash = "".join([hex(value)[2:].zfill(8) for value in self.hashes])
def ror(self, value: int, rotations: int) -> int:
"""
Right rotate a given unsigned number by a certain amount of rotations
"""
return 0xFFFFFFFF & (value << (32 - rotations)) | (value >> rotations)
class SHA256HashTest(unittest.TestCase):
"""
Test class for the SHA256 class. Inherits the TestCase class from unittest
"""
def test_match_hashes(self) -> None:
import hashlib
msg = bytes("Test String", "utf-8")
self.assertEqual(SHA256(msg).hash, hashlib.sha256(msg).hexdigest())
def main() -> None:
"""
Provides option 'string' or 'file' to take input
and prints the calculated SHA-256 hash
"""
# unittest.main()
import doctest
doctest.testmod()
parser = argparse.ArgumentParser()
parser.add_argument(
"-s",
"--string",
dest="input_string",
default="Hello World!! Welcome to Cryptography",
help="Hash the string",
)
parser.add_argument(
"-f", "--file", dest="input_file", help="Hash contents of a file"
)
args = parser.parse_args()
input_string = args.input_string
# hash input should be a bytestring
if args.input_file:
with open(args.input_file, "rb") as f:
hash_input = f.read()
else:
hash_input = bytes(input_string, "utf-8")
print(SHA256(hash_input).hash)
if __name__ == "__main__":
main()