authur1 idk what i did but changes
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25B4ACF7D88186CC
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@ -82,7 +82,7 @@ def authur1(input: bytearray, verbose: bool = False) -> bytearray:
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assert len(accumulator) == 4, "accumulator too long: %d bytes" % len(accumulator)
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if verbose:
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print("returning state: %s" % accumulator.hex())
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print("last internal state: %s" % accumulator.hex())
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# now Q the accumulator and return
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# if input = "" this step breaks things, just remove it.
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if len(input) != 0:
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@ -91,42 +91,34 @@ def authur1(input: bytearray, verbose: bool = False) -> bytearray:
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accumulator: bytearray = bytearray(accuint.to_bytes(4))
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return accumulator
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def test():
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init: int = int.from_bytes(DEFINED_INITIAL)
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a: int = inner_authur1(init)
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b: int = inner_authur1(a)
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c: int = inner_authur1(b)
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assert a == 0xded7e2d2, "Q(S0) returns wrong value: %s" % hex(a)
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assert b == 0x1b725f7d, "Q(Q(S0)) returns wrong value: %s" % hex(b)
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assert c == 0xa5886999, "Q(Q(Q(S0))) returns wrong value: %s" % hex(c)
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print("Q aka inner_authur1 passed the test")
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ha: bytearray = authur1(bytearray(0))
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hb: bytearray = authur1(bytearray(b'A'))
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hc: bytearray = authur1(bytearray(b'AB'))
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hd: bytearray = authur1(bytearray(b'ABC'))
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he: bytearray = authur1(bytearray(b'ABCD'))
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hf: bytearray = authur1(bytearray(b'ABCDE'))
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assert int.from_bytes(ha) == 0xded7e2d2, "H(\"\") returns wrong value: %s" % ha.hex()
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assert int.from_bytes(hb) == 0x5d725f7f, "H(\"A\") returns wrong value: %s" % hb.hex()
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assert int.from_bytes(hc) == 0x5f3b5f7f, "H(\"AB\") returns wrong value: %s" % hc.hex()
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assert int.from_bytes(hd) == 0x5f39137f, "H(\"ABC\") returns wrong value: %s" % hd.hex()
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assert int.from_bytes(he) == 0x5f391128, "H(\"ABCD\") returns wrong value: %s" % he.hex()
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assert int.from_bytes(hf) == 0x2f69af58, "H(\"ABCDE\") returns wrong value: %s" % hf.hex()
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print("H aka authur1 passed the test")
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test_extension_attack()
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print("All tests passed!")
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def keyed_hash(message: bytearray, key: bytearray) -> bytearray:
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assert len(key) == 16, "key is not 16 Byte long: %s" % len(key)
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# prepend only
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input: bytearray = key + message
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mic: bytearray = authur1(input)
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return mic
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def reverse_inner_authur1(output: int) -> int:
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assert output.bit_length() <= 32, "output length is <= 32: %d" % output.bit_length()
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# plexcryptool.binary uses u32 for shifting
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#output: int = input ^ (binary.rotl32(input, SHIFT_LENGTH))
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# -> output ^ input = binary.rotl32(input, SHIFT_LENGTH)
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# -> input = binary.rotl32(input, SHIFT_LENGTH) ^ output
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input: int = output ^ (binary.rotr32(output, SHIFT_LENGTH))
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assert False, "inner_authur1 can not be reversed!"
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assert input.bit_length() <= 32, "input length is <= 32: %d" % input.bit_length()
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return input
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def find_last_internal_state(mic: bytearray) -> bytearray:
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# reverse the mic to get the last internal state
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# TODO
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raise NotImplementedError("find last internal state is still TODO")
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return mic
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def extension_attack(valid_pairs: list):
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"""
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Extension attack against keyed hash of authur1
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@ -156,26 +148,66 @@ def extension_attack(valid_pairs: list):
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> Knowledge of the key is not necessary at all, yet valid forgeries can be
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> produced efficiently by the adversary
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find a valid message that has the right length (length % 16 == 0)
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use any convenient message that has low length?
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fill it with padding?
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-> internal block length is 4 byte
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-> we don't have one given in the exercise
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reverse the last state before finalizing in the hash
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-> we have a valid internal state and can continue to append our own whatever to it?
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-> But the mic at the end should change, right?
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(the exercise said the Key K has length 16, which is really handy, so i don't need to calculate for that.)
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(16 % 4 is 0)
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"""
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# find a valid message
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target_pair = None
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for msg, mic in valid_pairs:
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print("%s has length %s" % (msg, len(msg)))
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if len(msg) % 16 == 0:
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if len(msg) % 4 == 0:
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# we have a message of the right length!
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target_pair = (msg, mic)
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else:
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# for now, just use the first one?
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while len(msg) % 4 != 0:
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msg.append(PADDING)
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target_pair = (msg, mic)
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if target_pair is None:
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print("The given originals were not sufficient to perform an extension attack.\n"+
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"We need a message, which has a length that is a multiple of 16 (Bytes).")
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return
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print("Found a fitting target pair: %s" % target_pair)
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last_internal: bytearray = find_last_internal_state(target_pair[1])
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print("Found a fitting target pair: (%s,%s)" % target_pair)
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def test():
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init: int = int.from_bytes(DEFINED_INITIAL)
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a: int = inner_authur1(init)
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b: int = inner_authur1(a)
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c: int = inner_authur1(b)
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assert a == 0xded7e2d2, "Q(S0) returns wrong value: %s" % hex(a)
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assert b == 0x1b725f7d, "Q(Q(S0)) returns wrong value: %s" % hex(b)
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assert c == 0xa5886999, "Q(Q(Q(S0))) returns wrong value: %s" % hex(c)
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print("Q aka inner_authur1 passed the test")
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ha: bytearray = authur1(bytearray(0))
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hb: bytearray = authur1(bytearray(b'A'))
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hc: bytearray = authur1(bytearray(b'AB'))
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hd: bytearray = authur1(bytearray(b'ABC'))
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he: bytearray = authur1(bytearray(b'ABCD'))
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hf: bytearray = authur1(bytearray(b'ABCDE'))
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assert int.from_bytes(ha) == 0xded7e2d2, "H(\"\") returns wrong value: %s" % ha.hex()
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assert int.from_bytes(hb) == 0x5d725f7f, "H(\"A\") returns wrong value: %s" % hb.hex()
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assert int.from_bytes(hc) == 0x5f3b5f7f, "H(\"AB\") returns wrong value: %s" % hc.hex()
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assert int.from_bytes(hd) == 0x5f39137f, "H(\"ABC\") returns wrong value: %s" % hd.hex()
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assert int.from_bytes(he) == 0x5f391128, "H(\"ABCD\") returns wrong value: %s" % he.hex()
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assert int.from_bytes(hf) == 0x2f69af58, "H(\"ABCDE\") returns wrong value: %s" % hf.hex()
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print("H aka authur1 passed the test")
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test_reverse_inner_authur1()
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test_extension_attack()
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print("All tests passed!")
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def test_extension_attack():
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"""
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@ -184,9 +216,17 @@ def test_extension_attack():
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# TODO
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raise(NotImplementedError("Extension attack is still TODO"))
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def test_reverse_inner_authur1():
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a = 0x1337
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aq = inner_authur1(a)
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assert reverse_inner_authur1(aq) == a, "reverse_inner_authur1 does not work:\n%s\nis not\n%s" % (
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bin(a),
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bin(reverse_inner_authur1(a))
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)
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def main():
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parser = argparse.ArgumentParser(prog="authur1 authentication hash", description='Implementation and attack for the custom authur1 hash. Don\'t actually use this hash!')
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parser.add_argument('-i', '--hash', type=str,
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parser = argparse.ArgumentParser(prog="authur1", description='Implementation and attack for the custom authur1 hash. Don\'t actually use this hash!')
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parser.add_argument('-i', '--hash', type=str, metavar="MSG",
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help='an input that should be hashed')
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parser.add_argument('-k', '--key', type=str,
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help='an key that should be used with auth mode')
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@ -194,7 +234,7 @@ def main():
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help='perform tests')
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parser.add_argument('-v', '--verbose', action="store_true",
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help='print many things')
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parser.add_argument('-e', '--extension-attack', type=str,
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parser.add_argument('-e', '--extension-attack', metavar="ORIGINALS", type=str,
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help='perform an extension attack, this option requires known mics in the form: "msg1:deadbeed,msg2:abababab,msg3:ecbadf,..."')
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parser.add_argument('-a', '--auth', action="store_true",
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help='generate a message integrity code (mic), needs a value to be hashed. If no key is specified, a random key will be generated.')
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