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