[Python] I made a function that decrypts AES encryption just by throwing it with pycrypto.

What you can do -When executed with plaintext, password, and vector as arguments, data encrypted in base64 format is returned. -Similarly, if the plaintext is replaced with the data encrypted in the base64 format and executed, the plaintext is returned.

AES encryption conditions The key must be 16 bytes, 24 bytes, or 32 bytes long. Plaintext must be a multiple of 16 bytes. Use iv to make it harder to guess. Regarding iv, I think it is appropriate to use the same one for one application.

I think it's okay to copy and use it, but I can't guarantee that the code is correct because I don't fully understand AES. If you have any vulnerabilities, please let us know in the comments.

Installation is

$ pip install pycrypto

Encryption

get_encrypt_data.py

from Crypto.Cipher import AES
import hashlib
import base64

def get_encrypt_data(raw_data, key, iv):
    raw_data_base64 = base64.b64encode(raw_data)
    # 16byte
    if len(raw_data_base64) % 16 != 0:
        raw_data_base64_16byte = raw_data_base64
        for i in range(16 - (len(raw_data_base64) % 16)):
            raw_data_base64_16byte += "_"
    else:
        raw_data_base64_16byte = raw_data_base64
    secret_key = hashlib.sha256(key).digest()
    iv = hashlib.md5(iv).digest()
    crypto = AES.new(secret_key, AES.MODE_CBC, iv)
    cipher_data = crypto.encrypt(raw_data_base64_16byte)
    cipher_data_base64 = base64.b64encode(cipher_data)
    return cipher_data_base64

Plaintext data as an argument. key. vector. First of all, change to base64 (to make double-byte characters and images ok) Then the encrypted statement must be a multiple of 16 bits, so Basically, "_" that is not used in base64 is complemented with a ketsu and converted to a multiple of 16 bits. If it is a multiple of 16 bytes, it is as it is Change the key to 32 bit length with sha256. Change the vector to 16-bit length with MD5. Encrypt it, convert it to base64 for easy transmission, and return it.

Decryption

get_decrypt_data.py

from Crypto.Cipher import AES
import hashlib
import base64

def get_decrypt_data(cipher_data_base64, key, iv):
    cipher_data = base64.b64decode(cipher_data_base64)
    secret_key = hashlib.sha256(key).digest()
    iv = hashlib.md5(iv).digest()
    crypto = AES.new(secret_key, AES.MODE_CBC, iv)
    raw_data_base64_16byte = crypto.decrypt(cipher_data)
    raw_data_base64 = raw_data_base64_16byte.split("_")[0]
    raw_data = base64.b64decode(raw_data_base64)
    return raw_data

Cryptographic data converted to base64 as an argument. key. vector. First, convert the encrypted data converted to base64 into encrypted data. Then change the key to 32 bits with sha256. Decrypt and extract only valid base64 with split ("_") [0] and return it as a converted return.

Execution result

main.py

if __name__ == "__main__":
    message = "114514"
    password = "This is password"
    iv = "hoge"
    encrypt_data = get_encrypt_data(message, password, iv)
    print encrypt_data
    decrypt_data = get_decrypt_data(encrypt_data, password, iv)
    print decrypt_data

cmd.sh

$ r64FMFs04APfNQo2d6uFpQ==
$ 114514