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encrypting and decrypting with python and nodejs


encrypting and decrypting with python and nodejs  using -'python,node.js,encryption,aes'

I'm trying to encrypt some content in Python and decrypt it in a nodejs application.

I'm struggling to get the two AES implementations to work together though. Here is where I am at.

In node:

var crypto = require('crypto');

var password = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
var input = 'hello world';

var encrypt = function (input, password, callback) {
    var m = crypto.createHash('md5');
    m.update(password)
    var key = m.digest('hex');

    m = crypto.createHash('md5');
    m.update(password + key)
    var iv = m.digest('hex');

    // add padding
    while (input.length % 16 !== 0) {
        input += ' ';
    }

    var data = new Buffer(input, 'utf8').toString('binary');

    var cipher = crypto.createCipheriv('aes-256-cbc', key, iv.slice(0,16));
    var encrypted = cipher.update(data, 'binary') + cipher.final('binary');
    var encoded = new Buffer(encrypted, 'binary').toString('base64');

    callback(encoded);
};

var decrypt = function (input, password, callback) {
    // Convert urlsafe base64 to normal base64
    var input = input.replace('-', '+').replace('/', '_');
    // Convert from base64 to binary string
    var edata = new Buffer(input, 'base64').toString('binary')

    // Create key from password
    var m = crypto.createHash('md5');
    m.update(password)
    var key = m.digest('hex');

    // Create iv from password and key
    m = crypto.createHash('md5');
    m.update(password + key)
    var iv = m.digest('hex');

    // Decipher encrypted data
    var decipher = crypto.createDecipheriv('aes-256-cbc', key, iv.slice(0,16));
    var decrypted = decipher.update(edata, 'binary') + decipher.final('binary');
    var plaintext = new Buffer(decrypted, 'binary').toString('utf8');

    callback(plaintext);
};

encrypt(input, password, function (encoded) {
    console.log(encoded);
    decrypt(encoded, password, function (output) {
        console.log(output);
    });
});


This produces the output:

BXSGjDAYKeXlaRXVVJGuREKTPiiXeam8W9e96Nknt3E=
hello world


In python

from Crypto.Cipher import AES
from hashlib import md5
import base64

password = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
input = 'hello world'

def _encrypt(data, nonce, password):
    m = md5()
    m.update(password)
    key = m.hexdigest()

    m = md5()
    m.update(password + key)
    iv = m.hexdigest()

    # pad to 16 bytes
    data = data + " " * (16 - len(data) % 16)

    aes = AES.new(key, AES.MODE_CBC, iv[:16])

    encrypted = aes.encrypt(data)
    return base64.urlsafe_b64encode(encrypted)

def _decrypt(edata, nonce, password):
    edata = base64.urlsafe_b64decode(edata)

    m = md5()
    m.update(password)
    key = m.hexdigest()

    m = md5()
    m.update(password + key)
    iv = m.hexdigest()

    aes = AES.new(key, AES.MODE_CBC, iv[:16])
    return aes.decrypt(edata)

output = _encrypt(input, "", password)
print(output)
plaintext = _decrypt(output, "", password)
print(plaintext)


This produces the output

BXSGjDAYKeXlaRXVVJGuRA==
hello world


Clearly they are very close, but node seems to be padding the output with something. Any ideas how I can get the two to interoperate?
    
asked Sep 18, 2015 by thiru
0 votes
44 views



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