def base64_from_hex(_hex):
return codecs.encode(bytes.fromhex(_hex), 'base64').decode('utf-8')
-def hex_xor(hex0, hex1):
+def xor_bytes(bytes0, bytes1):
+ return bytes(b0 ^ b1 for b0, b1 in zip(bytes0, bytes1))
+
+def xor_hex(hex0, hex1):
assert len(hex0) == len(hex1)
bytes0 = bytes.fromhex(hex0)
bytes1 = bytes.fromhex(hex1)
- xored_bytes = bytes(byte0 ^ byte1 for byte0, byte1 in zip(bytes0, bytes1))
- return codecs.encode(xored_bytes, 'hex').decode('utf-8')
+ return codecs.encode(xor_bytes(bytes0, bytes1), 'hex').decode('utf-8')
+
+def get_character_frequencies(source):
+ frequencies = {}
+
+ for source_character in source:
+ frequencies[source_character] = frequencies.get(source_character, 0) + 1
+
+ return frequencies
+
+def compare_frequency_deviation(base_frequency, comparison_frequency):
+ return sum(
+ abs(frequency - comparison_frequency.get(character, 0))
+ for character, frequency in base_frequency.items()
+ ) / len(base_frequency)
+
+with open('sample.txt','r') as sample_file:
+ sample_text = sample_file.read()
+
+SAMPLE_FREQUENCIES = get_character_frequencies(sample_text)
+
+def encrypt_with_repeating_xor(plaintext, key):
+ plaintext_bytes = plaintext.encode('utf-8')
+ key_bytes = key.encode('utf-8')
+
+ return xor_bytes(
+ plaintext_bytes,
+ (key_bytes * ((len(plaintext_bytes) // len(key_bytes)) + 1))[:len(plaintext_bytes)],
+ )
+
+def hamming_weight(_bytes):
+ def hamming_weight_of_byte(b):
+ count = 0
+ while b > 0:
+ count += 1
+ b &= b - 1
+ return count
+
+ return sum(hamming_weight_of_byte(b) for b in _bytes)
+
+def hamming_distance(bytes0, bytes1):
+ return hamming_weight(xor_bytes(bytes0, bytes1))
class Set1Challenge1Tests(unittest.TestCase):
def test_converts_hex_to_base64(self):
hex1 = '686974207468652062756c6c277320657965'
expected = '746865206b696420646f6e277420706c6179'
- actual = hex_xor(hex0, hex1)
+ actual = xor_hex(hex0, hex1)
+
+ self.assertEqual(expected, actual)
+
+class Set1Challenge3Tests(unittest.TestCase):
+ def test_gets_message(self):
+ xored_string = bytes.fromhex('1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736')
+
+ lowest_frequency_deviation_string = None
+ lowest_frequency_deviation = None
+
+ for i in range(128):
+ key_char = bytes([i]).decode('utf-8')
+ key = bytes([i]) * len(xored_string)
+ try_string = xor_bytes(xored_string, key).decode('utf-8')
+ try_string_frequency_deviation = compare_frequency_deviation(
+ SAMPLE_FREQUENCIES,
+ get_character_frequencies(try_string),
+ )
+
+ if lowest_frequency_deviation is None or try_string_frequency_deviation < lowest_frequency_deviation:
+ lowest_frequency_deviation_string = try_string
+ lowest_frequency_deviation = try_string_frequency_deviation
+
+
+ expected = "Cooking MC's like a pound of bacon"
+ actual = lowest_frequency_deviation_string
+
+ self.assertEqual(expected, actual)
+
+class Set1Challenge4Tests(unittest.TestCase):
+ def test_gets_message(self):
+ with open('set1challenge4.txt','r') as f:
+ lines = f.readlines()
+
+
+ lowest_frequency_deviation_string = None
+ lowest_frequency_deviation = None
+
+ for line in lines:
+ line_bytes = bytes.fromhex(line)
+
+ for i in range(128):
+ key_char = bytes([i]).decode('utf-8')
+ key = bytes([i]) * len(line_bytes)
+
+ try:
+ try_string = xor_bytes(line_bytes, key).decode('utf-8')
+ try_string_frequency_deviation = compare_frequency_deviation(
+ SAMPLE_FREQUENCIES,
+ get_character_frequencies(try_string),
+ )
+
+ if lowest_frequency_deviation is None or try_string_frequency_deviation < lowest_frequency_deviation:
+ lowest_frequency_deviation_string = try_string
+ lowest_frequency_deviation = try_string_frequency_deviation
+ except:
+ pass
+
+ expected = 'Now that the party is jumping\n'
+ actual = lowest_frequency_deviation_string
+
+ self.assertEqual(expected, actual)
+
+class Set1Challenge5Tests(unittest.TestCase):
+ def test_encrypts_with_repeating_xor(self):
+ plaintext = "Burning 'em, if you ain't quick and nimble\nI go crazy when I hear a cymbal"
+ key = 'ICE'
+
+ expected = '0b3637272a2b2e63622c2e69692a23693a2a3c6324202d623d63343c2a26226324272765272a282b2f20430a652e2c652a3124333a653e2b2027630c692b20283165286326302e27282f'
+ actual = encrypt_with_repeating_xor(plaintext, key).hex()
+
+ self.assertEqual(expected, actual)
+
+with open('set1challenge6.txt','r') as f:
+ set1challenge6text = f.read()
+
+class Set1Challenge6Tests(unittest.TestCase):
+ def test_hamming_distance(self):
+ expected = 37
+ actual = hamming_distance(b'this is a test', b'wokka wokka!!!')
+ self.assertEqual(expected, actual)
+ def test_find_repeated_xor_keysize(self):
+ expected = 0
+ actual = find_repeated_xor_keysize(set1challenge6text)
self.assertEqual(expected, actual)
if __name__ == '__main__':