def p26():
user_data = 'A' * 16
comment1 = 'comment1=cooking%20MCs;userdata='
comment2 = ';comment2=%20like%20a%20pound%20of%20bacon'
ptxt = comment1 + user_data.replace(';', '').replace('=', '') + comment2
key = urandom(16)
ctxt = aes_ctr(ptxt, key)
ctxtmod = _bitflip(ctxt, user_data)
ptxtmod = aes_ctr(ctxtmod, key)
return _parse(ptxtmod)
def p25() -> bytes:
with open('Data/25.txt', 'rb') as f:
data = b64decode(f.read().replace(b'\n', b''))
key = b'YELLOW SUBMARINE'
ptxt = aes_ecb_decrypt(data, key)
key = urandom(16)
ctxt = aes_ctr(ptxt, key)
newtext = b'A' * len(ctxt)
edited = _edit_ctxt(ctxt, key, 0, newtext)
return xor(xor(edited, ctxt), newtext)
def p20() -> bytes:
key = urandom(16)
ctxts = []
with open('Data/20.txt', 'rb') as f:
for line in f.readlines():
ptxt = b64decode(line)
ctxts.append(aes_ctr(ptxt, key, 0))
keystream = b''
for i in range(min(map(len, ctxts))):
keystream += get_key([c[i] for c in ctxts])
ptxt = []
for ctxt in ctxts:
raw = [c ^ k for (c, k) in zip(ctxt, keystream)]
ptxt.append(bytes(raw))
return b'\n'.join(ptxt)
def p20():
key = urandom(16)
ctxts = []
with open('Data/20.txt') as f:
for line in f.readlines():
ptxt = b64decode(line)
ctxts.append(aes_ctr(ptxt, key, 0))
keystream = ''
for i in range(max(map(len, ctxts))):
keystream += get_key([(c[i] if i < len(c) else '') for c in ctxts])
ptxt = ''
for ctxt in ctxts:
raw = [chr(ord(c) ^ ord(k)) for (c, k) in zip(ctxt, keystream)]
ptxt += ''.join(raw) + '\n'
return ptxt[:-1]
def p19() -> bytes:
key = urandom(16)
ctxts = []
with open('Data/19.txt', 'rb') as f:
for line in f.readlines():
ptxt = b64decode(line)
ctxts.append(aes_ctr(ptxt, key, 0))
keystream = b''
for i in range(max(map(len, ctxts))):
index_bytes = [(c[i] if i < len(c) else None) for c in ctxts]
keystream += get_key(index_bytes)
ptxt = []
for ctxt in ctxts:
raw = [c ^ k for (c, k) in zip(ctxt, keystream)]
ptxt.append(bytes(raw))
return b'\n'.join(ptxt)
def _edit_ctxt(ctxt: bytes, key: bytes, offset: int, newtext: bytes) -> bytes:
new_ctxt = aes_ctr(newtext, key)
return ctxt[:offset] + new_ctxt + ctxt[offset + len(new_ctxt):]
