AES - Encryption with Crypto (node-js) / decryption with Pycrypto (python)

Question

I'm writing this question + answer because I struggled a lot (maybe because of a lack of experience), got lost in many different ways of encrypting/decrypting things with node or python. I thought maybe my case could help people in the future. What I needed to do: - Get data from a form, encrypt them using Crypto (node-js) - Pass the encrypted data in Python and decrypt it using PyCrypto. I chose to use the AES encryption. Here is how I started (I'm not gonna go through everything I tried): I followed the example at the end of this page Which gave in my case: (this might be a very bad mix between javascript and coffeescript) ``` crypto = require "crypto" [...] key = "mykeywhatever" cipher = crypto.createCipher('aes192', key) cipher.update('string i want to encode', 'binary', 'hex') encoded_string = cipher.final('hex') [...] ``` This worked pretty fine to encode my string. Then I wrote my python script to decrypt this string, using the readme on PyCrypto's github's page: ``` from Crypt…

Accepted Answer

So we started from the "How can i decrypt... OpenSSL" 's answer.

We needed to modify the encryption script which gave:

```
crypto = require "crypto"
[...]
var iv = new Buffer('asdfasdfasdfasdf')
var key = new Buffer('asdfasdfasdfasdfasdfasdfasdfasdf')
var cipher = crypto.createCipheriv('aes-256-cbc', key, iv);
cipher.update(new Buffer("mystring"));
var enc = cipher.final('base64');
[...]
```

iv needs to be 16bytes long, key is 32bytes. And we changed `createCipher` to `createCipheriv`.

Back to the python decryption script:

Process was simply reading PyCrypto's documentation, and compare with the code we started from.

Then we decided to just stick to the API, and start from scratch. And it gave:

```
from base64 import b64decode
from Crypto.Cipher import AES
[...]
iv = 'asdfasdfasdfasdf'
key = 'asdfasdfasdfasdfasdfasdfasdfasdf'
encoded = b64decode('my_encrypted_string')

dec = AES.new(key=key, mode=AES.MODE_CBC, IV=iv)
value = dec.decrypt(encoded)
```

And it was as simple as that... Hope it'll help some of you!

Update:

As Perseids wrote in the comments of his answer, the IV has to be random and different for every message

AES - Encryption with Crypto (node-js) / decryption with Pycrypto (python)

Solution

Problem