from Crypto.Cipher import AES
SUBMARINE_KEY = "YELLOW SUBMARINE"
def ECB_decrypt(content, key=SUBMARINE_KEY):
return AES.new(key, AES.MODE_ECB).decrypt(content)
def ECB_encrypt(content, key=SUBMARINE_KEY):
return AES.new(key, AES.MODE_ECB).encrypt(content)
if __name__ == "__main__":
import cryptopals as c
content = c.b64decode(open('data/7.txt').read())
assert ECB_encrypt(ECB_decrypt(content)) == content
print(ECB_decrypt(content))
SGUsIHRvbywgaGFzIGJlZW4gY2hhbmdlZCBpbiBoaXMgdHVybiw=
VHJhbnNmb3JtZWQgdXR0ZXJseTo=
QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=
"""
def solve_keystream(lines):
def best_char_for(index):
def score(char):
return sum(
c.character_frequencies.get(chr(line[index] ^ char), 0)
for line in lines if index < len(line))
return max(range(256), key=score)
return bytearray(map(best_char_for, range(max(map(len, lines)))))
def solve(lines, keystream):
for l in lines:
print(c.strxor(l, keystream))
if __name__ == "__main__":
lines = [c.CTR_Encrypt(c.b64decode(s)) for s in text.split('\n')[1:-1]]
keystream = solve_keystream(lines)
incorrect_idx = len(lines[0]) - 1
keystream[incorrect_idx] ^= (ord('u') ^ ord('y'))
solve(lines, keystream)
# poem is "Easter, 1916" by William Butler Yeats.
copy = bytearray(ciphertext)
final_offset = offset + len(newtext)
begin = round_down(offset)
end = round_up(final_offset)
encrypt = partial(c.CTR_Encrypt, key=key, offset=begin)
edited = bytearray(encrypt(ciphertext[begin:end]))
edited[offset - begin:final_offset - begin] = newtext
copy[begin:end] = encrypt(edited)
return bytes(copy)
def breakit(edit, ciphertext):
def get_char_at(idx):
for char in c.all_chars():
if edit(ciphertext, offset=idx, newtext=char) == ciphertext:
return char
raise ValueError("Couldn't break it!")
return b''.join(map(get_char_at, range(len(ciphertext))))
if __name__ == "__main__":
edit = partial(edit, key=c.RAND_KEY)
decrypt = encrypt = partial(c.CTR_Encrypt, key=c.RAND_KEY)
text = c.ECB_decrypt(c.b64decode(open('data/25.txt').read()))
print(text)
ciphertext = encrypt(text)
print(breakit(edit, ciphertext))
import cryptopals as c
from copy import copy
text = """MDAwMDAwTm93IHRoYXQgdGhlIHBhcnR5IGlzIGp1bXBpbmc=
MDAwMDAxV2l0aCB0aGUgYmFzcyBraWNrZWQgaW4gYW5kIHRoZSBWZWdhJ3MgYXJlIHB1bXBpbic=
MDAwMDAyUXVpY2sgdG8gdGhlIHBvaW50LCB0byB0aGUgcG9pbnQsIG5vIGZha2luZw==
MDAwMDAzQ29va2luZyBNQydzIGxpa2UgYSBwb3VuZCBvZiBiYWNvbg==
MDAwMDA0QnVybmluZyAnZW0sIGlmIHlvdSBhaW4ndCBxdWljayBhbmQgbmltYmxl
MDAwMDA1SSBnbyBjcmF6eSB3aGVuIEkgaGVhciBhIGN5bWJhbA==
MDAwMDA2QW5kIGEgaGlnaCBoYXQgd2l0aCBhIHNvdXBlZCB1cCB0ZW1wbw==
MDAwMDA3SSdtIG9uIGEgcm9sbCwgaXQncyB0aW1lIHRvIGdvIHNvbG8=
MDAwMDA4b2xsaW4nIGluIG15IGZpdmUgcG9pbnQgb2g=
MDAwMDA5aXRoIG15IHJhZy10b3AgZG93biBzbyBteSBoYWlyIGNhbiBibG93"""
strings = [c.b64decode(s) for s in text.split('\n')]
def cookie(string):
return (c.pad_CBC_encrypt(string, key=c.RAND_KEY), c.IV)
def decrypt(cookie):
return c.CBC_decrypt(cookie, key=c.RAND_KEY)
def check(cookie):
try:
c.remove_padding(decrypt(cookie))
except ValueError:
return False
return True
import cryptopals as c
from struct import pack
def CTR_Encrypt(text, key=c.RAND_KEY, offset=0):
text = c.as_bytes(text)
start_block = offset // 16
# limit to 2 ** 32 bytes transfereed
return b''.join(
c.strxor(
c.ECB_encrypt(
b'\x00' * 8 + pack("<l", i + start_block) + b'\x00' * 4,
key=key),
block)
for i, block in enumerate(c.blocks(text)))
if __name__ == "__main__":
print(CTR_Encrypt(c.b64decode('L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ=='), key=c.SUBMARINE_KEY))