test.py

#!/usr/bin/env python

from __future__ import print_function
# Standard library imports
import unittest
import random
import hashlib

try:
    range = xrange
except NameError:
    pass

# Custom SHA-1 library
import sha1

class TestSha1(unittest.TestCase):
    """TestSha1 class

    Test case for the custom SHA-1 implementation.
    """
    def test_similar(self):
        """Test Similar SHA-1 Inputs

        Tests sets of messages with 1 bit of difference. Ensures that all
        messages produce unique hashes.
        """
        print('\n>>> running: test_similar')
        first_msg = bytearray(get_random_bytes())
        modified_msg = bytearray()

        # Pick a random byte, modify it by one bit
        byte_to_modify = random.randrange(0, len(first_msg))

        for i, byte in enumerate(first_msg):
            augmentor = 1 if i == byte_to_modify else 0
            modified_msg.append(byte + augmentor)

        first_digest = sha1.sha1(bytes(first_msg))
        modified_digest = sha1.sha1(bytes(modified_msg))

        print('... test_similar: checking digest differences')
        self.assertNotEqual(first_digest, modified_digest)

        print('... test_similar: success')

    def test_repeatable(self):
        """Test SHA-1 Repeatability

        Runs the SHA-1 hashing function multiple times to ensure the same
        outcome for any identical message input.
        """
        print('\n>>> running: test_repeatable')
        msg = bytearray(get_random_bytes())

        first_digest = sha1.sha1(bytes(msg))
        second_digest = sha1.sha1(bytes(msg))

        print('... test_repeatable: checking for identical digests')
        self.assertEqual(first_digest, second_digest)

        print('... test_repeatable: success')

    def test_comparison(self):
        """Test SHA-1 Library Accuracy

        Runs the custom SHA-1 hashing function implementation with other
        SHA-1 functions contained in the Python hashlib library.
        """
        print('\n>>> running: test_comparison')
        msg = bytearray(get_random_bytes())

        custom_sha1_digest = sha1.sha1(bytes(msg))
        stdlib_sha1_digest = hashlib.sha1(bytes(msg)).hexdigest()

        print('... test_comparison: checking for identical digests')
        self.assertEqual(custom_sha1_digest, stdlib_sha1_digest)

        print('... test_comparison: success')

    def test_associativity(self):
        """Test SHA-1 associativity

        Tests the fact that sha1(ab) is equivalent to sha1(a) updated with b.
        """
        print('\n>>> running: test_associativity')
        msg1 = bytearray(get_random_bytes())
        msg2 = bytearray(get_random_bytes())

        first_digest = sha1.sha1(bytes(msg1) + bytes(msg2))

        sha = sha1.Sha1Hash()
        sha.update(msg1)
        sha.update(msg2)

        second_digest = sha.hexdigest()

        print('... test_associativity: checking for identical digests')
        self.assertEqual(first_digest, second_digest)

        print('... test_associativity: success')



def get_random_bytes():
    """Get Random Bits

    Generates a sequence of random bits of a random size between 1 and 1000
    bits in the sequence.

    Returns:
        A stream of random bits.
    """
    size = random.randrange(1, 1000)

    for _ in range(size):
        yield random.getrandbits(8)

if __name__ == '__main__':
    unittest.main()