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# Author: Trevor Perrin
# See the LICENSE file for legal information regarding use of this file.
"""Pure-Python AES implementation."""
from .cryptomath import *
from .aes import *
from .rijndael import rijndael
def new(key, mode, IV):
return Python_AES(key, mode, IV)
class Python_AES(AES):
def __init__(self, key, mode, IV):
AES.__init__(self, key, mode, IV, "python")
self.rijndael = rijndael(key, 16)
self.IV = IV
def encrypt(self, plaintext):
AES.encrypt(self, plaintext)
plaintextBytes = plaintext[:]
chainBytes = self.IV[:]
#CBC Mode: For each block...
for x in range(len(plaintextBytes)//16):
#XOR with the chaining block
blockBytes = plaintextBytes[x*16 : (x*16)+16]
for y in range(16):
blockBytes[y] ^= chainBytes[y]
#Encrypt it
encryptedBytes = self.rijndael.encrypt(blockBytes)
#Overwrite the input with the output
for y in range(16):
plaintextBytes[(x*16)+y] = encryptedBytes[y]
#Set the next chaining block
chainBytes = encryptedBytes
self.IV = chainBytes[:]
return plaintextBytes
def decrypt(self, ciphertext):
AES.decrypt(self, ciphertext)
ciphertextBytes = ciphertext[:]
chainBytes = self.IV[:]
#CBC Mode: For each block...
for x in range(len(ciphertextBytes)//16):
#Decrypt it
blockBytes = ciphertextBytes[x*16 : (x*16)+16]
decryptedBytes = self.rijndael.decrypt(blockBytes)
#XOR with the chaining block and overwrite the input with output
for y in range(16):
decryptedBytes[y] ^= chainBytes[y]
ciphertextBytes[(x*16)+y] = decryptedBytes[y]
#Set the next chaining block
chainBytes = blockBytes
self.IV = chainBytes[:]
return ciphertextBytes
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