def update(self, data, ed):
"""Processes the given ciphertext/plaintext
Inputs:
data: raw string of any length
ed: 'e' for encryption, 'd' for decryption
Output:
hashed data as raw string
This is not really an update function:
Everytime the function is called, the hash from the input data is calculated.
No finalizing needed.
"""
assert ed == 'e'
blocksize = self.blocksize
m = (len(data) + blocksize - 1) / blocksize #m = amount of datablocks
i = 0
for i in range(1, m):
self.IV = self.codebook.encrypt(
util.xorstring(data[(i - 1) * blocksize:(i) * blocksize],
self.IV))
if len(data[(i) * blocksize:]) == blocksize:
X = util.xorstring(util.xorstring(data[(i) * blocksize:], self.IV),
self.Lu)
else:
tmp = data[(i) *
blocksize:] + '\x80' + '\x00' * (blocksize - len(data[
(i) * blocksize:]) - 1)
X = util.xorstring(util.xorstring(tmp, self.IV), self.Lu2)
T = self.codebook.encrypt(X)
return T
def __xts_step(self, ed, tocrypt, T):
T_string = util.number2string_N(T, 16)[::-1]
# C = E_K1(P xor T) xor T
if ed == 'd':
return util.xorstring(
T_string,
self.codebook1.decrypt(util.xorstring(T_string, tocrypt)))
else:
return util.xorstring(
T_string,
self.codebook1.encrypt(util.xorstring(T_string, tocrypt)))
def update(self, data, ed):
"""Processes the given ciphertext/plaintext
Inputs:
data: raw string of any length
ed: 'e' for encryption, 'd' for decryption
Output:
processed raw string block(s), if any
When the supplied data is not a multiple of the blocksize
of the cipher, then the remaining input data will be cached.
The next time the update function is called with some data,
the new data will be concatenated to the cache and then
cache+data will be processed and full blocks will be outputted.
"""
if ed == 'e':
encrypted_blocks = ''
self.cache += data
if len(self.cache) < self.blocksize:
return ''
for i in xrange(0,
len(self.cache) - self.blocksize + 1,
self.blocksize):
self.IV = self.codebook.encrypt(
util.xorstring(self.cache[i:i + self.blocksize], self.IV))
encrypted_blocks += self.IV
self.cache = self.cache[i + self.blocksize:]
return encrypted_blocks
else:
decrypted_blocks = ''
self.cache += data
if len(self.cache) < self.blocksize:
return ''
for i in xrange(0,
len(self.cache) - self.blocksize + 1,
self.blocksize):
plaintext = util.xorstring(
self.IV,
self.codebook.decrypt(self.cache[i:i + self.blocksize]))
self.IV = self.cache[i:i + self.blocksize]
decrypted_blocks += plaintext
self.cache = self.cache[i + self.blocksize:]
return decrypted_blocks