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javascriptpythonaespycryptocryptojs

Making CryptoJS and pycrypto compatible

I'm trying to figure out how to use the CryptoJS library for AES but the documentation is somewhat scarce.

I've followed their example but I can't seem to decode something that I encoded in PyCrypto

I've formatted as follows:

key = '0f3f0fe38eb5f216cb4ef0649f81d761'
ciphertext = 'Y+gwBI6R37Ko1lQmwZ57gg==FqUSqQ=='

The ciphertext has two components

iv: Y+gwBI6R37Ko1lQmwZ57gg==
encoded message: FqUSqQ==

I tried running the code below but it didn't work. It logs "" in the console. It should be resolving to 'Test'

var decrypted =CryptoJS.AES.decrypt(ciphertext, key);
console.log( decrypted.toString(CryptoJS.enc.Utf8) );

Any pointers would great. Thanks

Solution

  • I ran into this problem as well and unfortunately it was very tricky to get pycrypto to talk to crypto-js. Here are the combination that worked for me:

    1. Use MODE_CFB with segment_size=128 when encrypting in Python
    2. You must pad your string with Pkcs7 as per RFC 2315 [Page 21]
    3. Once you have received the base64 version of ciphertext in JS, you need to wrap it in CryptoJS.lib.CipherParams.create({ ... })

    Take a look at the code that works for me (Python 2.7.x):
    https://gist.github.com/marcoslin/8026990