from
Crypto
.
Cipher
import
AES
import
os
def
encrypt_file
(
key
,
filename
)
:
chunksize
=
64
*
1024
outputFile
=
"(encrypted)"
+
filename
    filesize
=
str
(
os
.
path
.
getsize
(
filename
)
)
.
zfill
(
16
)
IV
=
os
.
urandom
(
16
)
encryptor
=
AES
.
new
(
key
,
AES
.
MODE_CBC
,
IV
)
with
open
(
filename
,
'rb'
)
as
infile
:
with
open
(
outputFile
,
'wb'
)
as
outfile
:
outfile
.
write
(
filesize
.
encode
(
'utf-8'
)
)
outfile
.
write
(
IV
)
while
True
:
chunk
=
infile
.
read
(
chunksize
)
if
len
(
chunk
)
==
0
:
break
elif
len
(
chunk
)
%
16
!=
0
:
chunk
+=
b' '
*
(
16
-
(
len
(
chunk
)
%
16
)
)
outfile
.
write
(
encryptor
.
encrypt
(
chunk
)
)
def
decrypt_file
(
key
,
filename
)
:
chunksize
=
64
*
1024
outputFile
=
filename
[
11
:
]
with
open
(
filename
,
'rb'
)
as
infile
:
filesize
=
int
(
infile
.
read
(
16
)
)
IV
=
infile
.
read
(
16
)
decryptor
=
AES
.
new
(
key
,
AES
.
MODE_CBC
,
IV
)
with
open
(
outputFile
,
'wb'
)
as
outfile
:
while
True
:
chunk
=
infile
.
read
(
chunksize
)
if
len
(
chunk
)
==
0
:
break
outfile
.
write
(
decryptor
.
decrypt
(
chunk
)
)
outfile
.
truncate
(
filesize
)
key
=
b'Sixteen byte key'
filename
=
'example.txt'
encrypt_file
(
key
,
filename
)
encrypted_filename
=
"(encrypted)example.txt"
decrypt_file
(
key
,
encrypted_filename
)