AES encryption example using M2Crypto module

m2crypto_aes.py

import sys
import base64
from M2Crypto import Rand, EVP

ENC_METHOD="aes_256_cbc"
MODE_B64, MODE_BIN = 0, 1
IV_LEN = 16

def encrypt(s, key, mode=MODE_BIN):
    iv = Rand.rand_bytes(IV_LEN)   # can be : iv = os.urandom(IV_LEN)
    cipher = EVP.Cipher(ENC_METHOD, key=key, iv=iv, op=1)
    v = cipher.update(s)
    v = iv + v + cipher.final()
    if mode == MODE_B64:
        v = base64.urlsafe_b64encode(v)
    return v

def decrypt(s, key, mode=MODE_BIN):
    if mode == MODE_B64:
        s = base64.urlsafe_b64decode(s)
    iv = s[:IV_LEN]
    cipher = EVP.Cipher(ENC_METHOD, key=key, iv=iv, op=0)
    v = cipher.update(s[IV_LEN:])
    v = v + cipher.final()
    return v

if __name__ == "__main__":
    passwd = 'mypassword'
    s = encrypt('test data for m2crypto encryption & decryption', passwd, mode=MODE_B64)
    print len(s), repr(s)
    s = decrypt(s, passwd, mode=MODE_B64)
    print len(s), repr(s)