def decrypt(self, ct: bytes) -> bytes: blks = ([self.IV]+split_blocks(ct, 16))[::-1] prev = self.decrypt_ecb(blks[0]) for i in blks[1:]: self.pt += [xor(i,prev)] prev = self.decrypt_ecb(i) return pkcs7_unpad(b''.join(self.pt[::-1]))
def encrypt(self, pt: bytes) -> bytes: blks = [self.IV]+split_blocks(pkcs7_pad(pt, 16), 16) prev = blks[0] for i in blks[1:]: self.ct += [self.encrypt_ecb(xor(prev,i))] prev = self.ct[-1] return b''.join(self.ct)
def ctr_break():
key = urandom(16)
ct = [ctr(i, key, nonce) for i in pt]
x = repeated_xor(b''.join(
[j for i in ct for j in split_blocks(i) if (len(j) == 16)]))
key = split_blocks(x.find_key(x.find_key_size()))[0]
return [xor(i, key) for i in ct] == pt
#!/usr/bin/python3
from Cryptopals import xor
if __name__ == '__main__':
a = '1c0111001f010100061a024b53535009181c'
b = '686974207468652062756c6c277320657965'
assert xor(
bytes.fromhex(a),
bytes.fromhex(b)).hex() == '746865206b696420646f6e277420706c6179'
def solve_xor(cip: bytes) -> bytes:
scr = [get_english_score(xor(cip, bytes([i]))) for i in range(255)]
return bytes([scr.index(max(scr))])
#!/usr/bin/python3
from Cryptopals import xor, get_english_score
def solve_xor(cip: bytes) -> bytes:
scr = [get_english_score(xor(cip, bytes([i]))) for i in range(255)]
return bytes([scr.index(max(scr))])
if __name__ == '__main__':
cip = bytes.fromhex(
'1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736')
assert xor(cip, solve_xor(cip)) == b"Cooking MC's like a pound of bacon"
#!/usr/bin/python3
from Cryptopals import xor
inp = b"Burning 'em, if you ain't quick and nimble\nI go crazy when I hear a cymbal"
key = b"ICE"
res = "0b3637272a2b2e63622c2e69692a23693a2a3c6324202d623d63343c2a26226324272765272a282b2f20430a652e2c652a3124333a653e2b2027630c692b20283165286326302e27282f"
if __name__ == '__main__':
assert xor(inp, key).hex() == res
def cipher(pt, seed):
prng = mersenne(seed)
key = b''.join([bytes([(prng.next()) % 1 << 8]) for _ in range(len(pt))])
print(key)
return xor(pt, key)
def ctr(ct: bytes, key: bytes, counter) -> bytes:
ret = b''
for j, i in enumerate(split_blocks(ct)):
ret += xor(ecb_encrypt(counter(j), key, False), i)
return ret[:len(ct)]
def find_key_size(cip: bytes) -> bytes:
normalized_val_list = []
for key_size in KEYSIZE:
blocks = split_blocks(cip, key_size)[:-1]
avg_ham_dist = sum(func_blocks(blocks,
hamming_dist)) / (len(blocks) - 1)
normalized_val_list += [avg_ham_dist / key_size]
return normalized_val_list.index(min(normalized_val_list)) + KEYSIZE[0]
byte_split_blocks = lambda blocks, key: b"".join(
[bytes([blk[key]]) for blk in blocks])
def find_key(cip: bytes, key_size: bytes) -> bytes:
blocks = split_blocks(cip, key_size)[:-1]
return b"".join(
[solve_xor(byte_split_blocks(blocks, i)) for i in range(key_size)])
def break_repeated_xor(cip: bytes) -> bytes:
return find_key(cip, find_key_size(cip))
if __name__ == '__main__':
cip = b64decode(open('6.txt', 'r').read())
plt = b64decode(open('6_sol.txt', 'r').read())
assert xor(cip, break_repeated_xor(cip)) == plt
