def encrypt(data, key, iv):
if (type(data) != str) & (type(data) != bytes):
raise ValueError('Data is neither string nor bytes!')
bsize = len(key)
if len(data) % bsize != 0:
raise ValueError('Length of data is not multiple of length of key!')
if len(iv) != bsize:
raise ValueError('Length of iv is not same as length of key!')
blocks = [
data[i:i + bsize] for i in range(0,
len(data) - bsize + 1, bsize)
]
cipher = Cipher(algorithms.AES(key),
modes.ECB(),
backend=default_backend())
ctext_blocks = [iv]
for i in range(0, len(blocks)):
cur = blocks[i]
prev = ctext_blocks[i]
cur = bxor(cur, prev)
cur = cipher.encryptor().update(cur)
ctext_blocks.append(cur)
ctext_blocks.pop(0) # because this would be the iv block
return b''.join(ctext_blocks)
def decrypt(data, desired):
dat = data[len(data) - bsize:len(data)]
result = [dat]
for i in range(len(data), 0, -bsize):
des = desired[i - bsize:i]
decrypted_dat = CBC.decrypt(dat, key, iv)
dat = bxor(des, decrypted_dat)
result.append(dat)
result.reverse()
result = b"".join(result)
return CBC.decrypt(result, key, iv)
def main():
filename = '10.txt'
with open(filename, 'r') as f:
data = b''.join((base64.b64decode(x.strip()) for x in f.readlines()))
key = b'YELLOW SUBMARINE'
iv = b'\x00' * len(key)
# decrypt the test file
d = decrypt(data, key, iv)
with open(filename + '.out', 'wb') as outf:
outf.write(d)
# then encrypt it again and diff
e = encrypt(d, key, iv)
if e == data:
print("VERIFIED!")
else:
print("ERROR - original differs from encrypted")
print(bxor(d, e))
def encrypt(data, key, iv):
bsize = len(key)
blocks = [
data[i:i + bsize] for i in range(0,
len(data) - bsize + 1, bsize)
]
cipher = Cipher(algorithms.AES(key),
modes.ECB(),
backend=default_backend())
ctext_blocks = [iv]
for i in range(0, len(blocks)):
cur = blocks[i]
prev = ctext_blocks[i]
cur = bxor(cur, prev)
cur = cipher.encryptor().update(cur)
ctext_blocks.append(cur)
ctext_blocks.pop(0) # because this would be the iv block
return b''.join(ctext_blocks)
def decrypt(data, key, iv):
if type(data) != bytes:
raise ValueError('Data is not bytes type!')
if type(key) != bytes:
raise ValueError('Key is not bytes type!')
if type(iv) != bytes:
raise ValueError('iv is not bytes type!')
data = iv + data
bsize = len(key)
if len(data) % bsize != 0:
raise ValueError('Length of data is not a multiple of length of key!')
if len(iv) != bsize:
raise ValueError('Length of iv is not same as length of key!')
blocks = [
data[i:i + bsize] for i in range(0,
len(data) - bsize + 1, bsize)
]
cipher = Cipher(algorithms.AES(key),
modes.ECB(),
backend=default_backend())
ptext_blocks = []
for i in range(len(blocks) - 1, 0, -1):
cur = blocks[i]
prev = blocks[i - 1]
cur = cipher.decryptor().update(cur)
cur = bxor(cur, prev)
ptext_blocks.append(cur)
ptext_blocks.reverse()
return b''.join(ptext_blocks)
def decrypt(data, key, iv):
data = iv + data
bsize = len(key)
blocks = [
data[i:i + bsize] for i in range(0,
len(data) - bsize + 1, bsize)
]
cipher = Cipher(algorithms.AES(key),
modes.ECB(),
backend=default_backend())
ptext_blocks = []
for i in range(len(blocks) - 1, 0, -1):
cur = blocks[i]
prev = blocks[i - 1]
cur = cipher.decryptor().update(cur)
cur = bxor(cur, prev)
ptext_blocks.append(cur)
ptext_blocks.reverse()
return b''.join(ptext_blocks)