I need to encrypt a string using AES encryption. This encryption was happening in C# earlier, but it needs to be converted into JavaScript (will be run on a browser).
The current code in C# for encryption is as following -
public static string EncryptString(string plainText, string encryptionKey)
{
byte[] clearBytes = Encoding.Unicode.GetBytes(plainText);
using (Aes encryptor = Aes.Create())
{
Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(encryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
encryptor.Key = pdb.GetBytes(32);
encryptor.IV = pdb.GetBytes(16);
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
{
cs.Write(clearBytes, 0, clearBytes.Length);
cs.Close();
}
plainText = Convert.ToBase64String(ms.ToArray());
}
}
return plainText;
}
I have tried to use CryptoJS to replicate the same functionality, but it's not giving me the equivalent encrypted base64 string. Here's my CryptoJS code -
function encryptString(encryptString, secretKey) {
var iv = CryptoJS.enc.Hex.parse('Ivan Medvedev');
var key = CryptoJS.PBKDF2(secretKey, iv, { keySize: 256 / 32, iterations: 500 });
var encrypted = CryptoJS.AES.encrypt(encryptString, key,{iv:iv);
return encrypted;
}
The encrypted string has to be sent to a server which will be able to decrypt it. The server is able to decrypt the encrypted string generated from the C# code, but not the encrypted string generated from JS code. I tried to compare the encrypted strings generated by both the code and found that the C# code is generating longer encrypted strings. For example keeping 'Example String' as plainText and 'Example Key' as the key, I get the following result -
C# - eAQO+odxOdGlNRB81SHR2XzJhyWtz6XmQDko9HyDe0w=
JS - 9ex5i2g+8iUCwdwN92SF+A==
The length of JS encrypted string is always shorter than the C# one. Is there something I am doing wrong? I just have to replicated the C# code into the JS code.
Update:
My current code after Zergatul's answer is this -
function encryptString(encryptString, secretKey) {
var keyBytes = CryptoJS.PBKDF2(secretKey, 'Ivan Medvedev', { keySize: 48 / 4, iterations: 1000 });
console.log(keyBytes.toString());
// take first 32 bytes as key (like in C# code)
var key = new CryptoJS.lib.WordArray.init(keyBytes.words, 32);
// skip first 32 bytes and take next 16 bytes as IV
var iv = new CryptoJS.lib.WordArray.init(keyBytes.words.splice(32 / 4), 16);
console.log(key.toString());
console.log(iv.toString());
var encrypted = CryptoJS.AES.encrypt(encryptString, key, { iv: iv });
return encrypted;
}
As illustrated in his/her answer that if the C# code converts the plainText into bytes using ASCII instead of Unicode, both the C# and JS code will produce exact results. But since I am not able to modify the decryption code, I have to convert the code to be equivalent of the original C# code which was using Unicode.
So, I tried to see, what's the difference between both the bytes array between ASCII and Unicode byte conversion in C#. Here's what I found -
ASCII Byte Array: [69,120,97,109,112,108,101,32,83,116, 114, 105, 110, 103]
Unicode Byte Array: [69,0,120,0,97,0,109,0,112,0,108,0,101,0,32,0,83,0,116,0, 114,0, 105,0, 110,0, 103,0]
So some extra bytes are available for each character in C# (So Unicode allocates twice as much bytes to each character than ASCII).
Here's the difference between both Unicode and ASCII conversion respectively -
ASCII
clearBytes: [69,120,97,109,112,108,101,32,83,116,114,105,110,103,]
encryptor.Key: [123,213,18,82,141,249,182,218,247,31,246,83,80,77,195,134,230,92,0,125,232,210,135,115,145,193,140,239,228,225,183,13,]
encryptor.IV: [101,74,46,177,46,233,68,252,83,169,211,13,249,61,118,167,]
Result: eQus9GLPKULh9vhRWOJjog==
Unicode:
clearBytes: [69,0,120,0,97,0,109,0,112,0,108,0,101,0,32,0,83,0,116,0,114,0,105,0,110,0,103,0,]
encryptor.Key: [123,213,18,82,141,249,182,218,247,31,246,83,80,77,195,134,230,92,0,125,232,210,135,115,145,193,140,239,228,225,183,13,]
encryptor.IV: [101,74,46,177,46,233,68,252,83,169,211,13,249,61,118,167,]
Result: eAQO+odxOdGlNRB81SHR2XzJhyWtz6XmQDko9HyDe0w=
So since both the key and iv being generated have exact same byte array in both Unicode and ASCII approach, it should not have generated different output, but somehow it's doing that. I think it's because of clearBytes' length, as it's using its length to write to CryptoStream.
I tried to see what's the output of the generated bytes in the JS code is and found that it uses words which needed to be converted into Strings using toString() method.
keyBytes: 7bd512528df9b6daf71ff653504dc386e65c007de8d2877391c18cefe4e1b70d654a2eb12ee944fc53a9d30df93d76a7
key: 7bd512528df9b6daf71ff653504dc386e65c007de8d2877391c18cefe4e1b70d
iv: 654a2eb12ee944fc53a9d30df93d76a7
Since, I am not able to affect the generated encrypted string's length in the JS code (No access to the write stream directly), thus still stuck here.
Here is the example how to reproduce the same ciphertext between C# and CryptoJS:
static void Main(string[] args)
{
byte[] plainText = Encoding.Unicode.GetBytes("Example String"); // this is UTF-16 LE
string cipherText;
using (Aes encryptor = Aes.Create())
{
var pdb = new Rfc2898DeriveBytes("Example Key", Encoding.ASCII.GetBytes("Ivan Medvedev"));
encryptor.Key = pdb.GetBytes(32);
encryptor.IV = pdb.GetBytes(16);
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
{
cs.Write(plainText, 0, plainText.Length);
cs.Close();
}
cipherText = Convert.ToBase64String(ms.ToArray());
}
}
Console.WriteLine(cipherText);
}
And JS:
var keyBytes = CryptoJS.PBKDF2('Example Key', 'Ivan Medvedev', { keySize: 48 / 4, iterations: 1000 });
// take first 32 bytes as key (like in C# code)
var key = new CryptoJS.lib.WordArray.init(keyBytes.words, 32);
// skip first 32 bytes and take next 16 bytes as IV
var iv = new CryptoJS.lib.WordArray.init(keyBytes.words.splice(32 / 4), 16);
// use the same encoding as in C# code, to convert string into bytes
var data = CryptoJS.enc.Utf16LE.parse("Example String");
var encrypted = CryptoJS.AES.encrypt(data, key, { iv: iv });
console.log(encrypted.toString());
Both codes return: eAQO+odxOdGlNRB81SHR2XzJhyWtz6XmQDko9HyDe0w=
TL;DR the final code looks like this -
function encryptString(encryptString, secretKey) {
encryptString = addExtraByteToChars(encryptString);
var keyBytes = CryptoJS.PBKDF2(secretKey, 'Ivan Medvedev', { keySize: 48 / 4, iterations: 1000 });
console.log(keyBytes.toString());
var key = new CryptoJS.lib.WordArray.init(keyBytes.words, 32);
var iv = new CryptoJS.lib.WordArray.init(keyBytes.words.splice(32 / 4), 16);
var encrypted = CryptoJS.AES.encrypt(encryptString, key, { iv: iv, });
return encrypted;
}
function addExtraByteToChars(str) {
let strResult = '';
for (var i = 0; i < str.length; ++i) {
strResult += str.charAt(i) + String.fromCharCode(0);
}
return strResult;
}
Explanation:
The C# code in the Zergatul's answer (Thanks to him/her) was using ASCII to convert the plainText into bytes, while my C# code was using Unicode. Unicode was assigning extra byte to each character in the resultant byte array, which was not affecting the generation of both key and iv bytes, but affecting the result since the length of the encryptedString was dependent on the length of the bytes generated from plainText.
As seen in the following bytes generated for each of them using "Example String" and "Example Key" as the plainText and secretKey respectively -
ASCII
clearBytes: [69,120,97,109,112,108,101,32,83,116,114,105,110,103,]
encryptor.Key: [123,213,18,82,141,249,182,218,247,31,246,83,80,77,195,134,230,92,0,125,232,210,135,115,145,193,140,239,228,225,183,13,]
encryptor.IV: [101,74,46,177,46,233,68,252,83,169,211,13,249,61,118,167,]
Result: eQus9GLPKULh9vhRWOJjog==
Unicode:
clearBytes: [69,0,120,0,97,0,109,0,112,0,108,0,101,0,32,0,83,0,116,0,114,0,105,0,110,0,103,0,]
encryptor.Key: [123,213,18,82,141,249,182,218,247,31,246,83,80,77,195,134,230,92,0,125,232,210,135,115,145,193,140,239,228,225,183,13,]
encryptor.IV: [101,74,46,177,46,233,68,252,83,169,211,13,249,61,118,167,]
Result: eAQO+odxOdGlNRB81SHR2XzJhyWtz6XmQDko9HyDe0w=
The JS result was similar too, which confirmed that it's using ASCII byte conversion -
keyBytes: 7bd512528df9b6daf71ff653504dc386e65c007de8d2877391c18cefe4e1b70d654a2eb12ee944fc53a9d30df93d76a7
key: 7bd512528df9b6daf71ff653504dc386e65c007de8d2877391c18cefe4e1b70d
iv: 654a2eb12ee944fc53a9d30df93d76a7
Thus I just need to increase the length of the plainText to make it use Unicode equivalent byte generation (Sorry, not familiar with the term). Since Unicode was assigning 2 space for each character in the byteArray, keeping the second space as 0, I basically created gap in the plainText's characters and filled that gap with character whose ASCII value was 0 using the addExtraByteToChars() function. And it made all the difference.
It's a workaround for sure, but started working for my scenario. I suppose this may or may not prove useful to others, thus sharing the findings. If anyone can suggest better implementation of the addExtraByteToChars() function (probably some term for this conversion instead of ASCII to Unicode or a better, efficient, and not hacky way to do that), please suggest it.
I have need to simply encrypt some text in python and being able to decrypt in JavaScrypt.
So far I have in python:
from Crypto import Random
from Crypto.Cipher import AES
import base64
BLOCK_SIZE = 16
key = "1234567890123456" # want to be 16 chars
textToEncrypt = "This is text to encrypt"
def encrypt(message, passphrase):
# passphrase MUST be 16, 24 or 32 bytes long, how can I do that ?
IV = Random.new().read(BLOCK_SIZE)
aes = AES.new(passphrase, AES.MODE_CFB, IV)
return base64.b64encode(aes.encrypt(message))
def decrypt(encrypted, passphrase):
IV = Random.new().read(BLOCK_SIZE)
aes = AES.new(passphrase, AES.MODE_CFB, IV)
return aes.decrypt(base64.b64decode(encrypted))
print encrypt( textToEncrypt, key )
this is producing text: ZF9as5JII5TlqcB5tAd4sxPuBXd5TrgE
in JavaScript:
<script src="http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/aes.js"></script>
<script>
var decrypted = CryptoJS.AES.decrypt( "ZF9as5JII5TlqcB5tAd4sxPuBXd5TrgE", "1234567890123456");
console.log ( decrypted.toString( CryptoJS.enc.Utf8 ) );
</script>
however it does not produce original string (empty string instead).
What I am doing wrong ?
Is it focusing on AES is a best idea - I will be happy if I have some kind of encryption that will blur data.
There are many problems with your Python code and CryptoJS code:
You use a random IV to encrypt some plaintext in Python. If you want to retrieve that plaintext, you need to use the same IV during decryption. The plaintext cannot be recovered without the IV. Usually the IV is simply prepended to the ciphertext, because it doesn't have to be secret. So you need to read the IV during decryption and not generate a new one.
You use CBC mode in CryptoJS (default) instead of CFB mode. The mode has to be the same. The other tricky part is that CFB mode is parametrized with a segment size. PyCrypto uses by default 8-bit segments (CFB8), but CryptoJS is only implemented for fixed segments of 128-bit (CFB128). Since the PyCrypto version is variable, you need to change that.
The CryptoJS decrypt() function expects as ciphertext either an OpenSSL formatted string or a CipherParams object. Since you don't have an OpenSSL formatted string, you have to convert the ciphertext into an object.
The key for CryptoJS is expected to be a WordArray and not a string.
Use the same padding. PyCrypto doesn't pad the plaintext if CFB8 is used, but padding is needed when CFB128 is used. CryptoJS uses PKCS#7 padding by default, so you only need to implement that padding in python.
Python code (for version 2):
def pad(data):
length = 16 - (len(data) % 16)
return data + chr(length)*length
def unpad(data):
return data[:-ord(data[-1])]
def encrypt(message, passphrase):
IV = Random.new().read(BLOCK_SIZE)
aes = AES.new(passphrase, AES.MODE_CFB, IV, segment_size=128)
return base64.b64encode(IV + aes.encrypt(pad(message)))
def decrypt(encrypted, passphrase):
encrypted = base64.b64decode(encrypted)
IV = encrypted[:BLOCK_SIZE]
aes = AES.new(passphrase, AES.MODE_CFB, IV, segment_size=128)
return unpad(aes.decrypt(encrypted[BLOCK_SIZE:]))
JavaScript code:
<script src="https://cdn.rawgit.com/CryptoStore/crypto-js/3.1.2/build/rollups/aes.js"></script>
<script src="https://cdn.rawgit.com/CryptoStore/crypto-js/3.1.2/build/components/mode-cfb-min.js"></script>
<script>
var base64ciphertextFromPython = "...";
var ciphertext = CryptoJS.enc.Base64.parse(base64ciphertextFromPython);
// split iv and ciphertext
var iv = ciphertext.clone();
iv.sigBytes = 16;
iv.clamp();
ciphertext.words.splice(0, 4); // delete 4 words = 16 bytes
ciphertext.sigBytes -= 16;
var key = CryptoJS.enc.Utf8.parse("1234567890123456");
// decryption
var decrypted = CryptoJS.AES.decrypt({ciphertext: ciphertext}, key, {
iv: iv,
mode: CryptoJS.mode.CFB
});
console.log ( decrypted.toString(CryptoJS.enc.Utf8));
</script>
Other considerations:
It seems that you want to use a passphrase as a key. Passphrases are usually human readable, but keys are not. You can derive a key from a passphrase with functions such as PBKDF2, bcrypt or scrypt.
The code above is not fully secure, because it lacks authentication. Unauthenticated ciphertexts may lead to viable attacks and unnoticed data manipulation. Usually the an encrypt-then-MAC scheme is employed with a good MAC function such as HMAC-SHA256.
(1 Year later but I hope this works for someone)
First of all, thanks Artjom B. your post helps me a lot. And Like OP, I have the same same problem Python server endonding and Javascript client decoding. This was my solution:
Python 3.x (Server)
I used an excplicit PKCS7 encode for padding, why? because I want to be sure Im using the same padding enconding and decoding, this is the link where I found it http://programmerin.blogspot.com.co/2011/08/python-padding-with-pkcs7.html .
Then, like Artjom B. said, be sure about your segment size, IV size and AES mode (CBC for me),
This is the code:
def encrypt_val(clear_text):
master_key = '1234567890123456'
encoder = PKCS7Encoder()
raw = encoder.encode(clear_text)
iv = Random.new().read( 16 )
cipher = AES.new( master_key, AES.MODE_CBC, iv, segment_size=128 )
return base64.b64encode( iv + cipher.encrypt( raw ) )
Note than your are enconding on base64 the concatenation of IV and encryption data.
Javascript (client)
function decryptMsg (data) {
master_key = '1234567890123456';
// Decode the base64 data so we can separate iv and crypt text.
var rawData = atob(data);
// Split by 16 because my IV size
var iv = rawData.substring(0, 16);
var crypttext = rawData.substring(16);
//Parsers
crypttext = CryptoJS.enc.Latin1.parse(crypttext);
iv = CryptoJS.enc.Latin1.parse(iv);
key = CryptoJS.enc.Utf8.parse(master_key);
// Decrypt
var plaintextArray = CryptoJS.AES.decrypt(
{ ciphertext: crypttext},
key,
{iv: iv, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7}
);
// Can be Utf8 too
output_plaintext = CryptoJS.enc.Latin1.stringify(plaintextArray);
console.log("plain text : " + output_plaintext);
}
One of my main problem was keep in mind all kind of encoding and decoding data, for example, I didn't know that the master_key on client side was to be parse with Utf8.
//First pip install pycryptodome -- (pycrypto is obsolete and gives issues)
// pip install pkcs7
from Crypto import Random
from Crypto.Cipher import AES
import base64
from pkcs7 import PKCS7Encoder
from app_settings.views import retrieve_settings # my custom settings
app_secrets = retrieve_settings(file_name='secrets');
def encrypt_data(text_data):
#limit to 16 bytes because my encryption key was too long
#yours could just be 'abcdefghwhatever'
encryption_key = app_secrets['ENCRYPTION_KEY'][:16];
#convert to bytes. same as bytes(encryption_key, 'utf-8')
encryption_key = str.encode(encryption_key);
#pad
encoder = PKCS7Encoder();
raw = encoder.encode(text_data) # Padding
iv = Random.new().read(AES.block_size ) #AES.block_size defaults to 16
# no need to set segment_size=BLAH
cipher = AES.new( encryption_key, AES.MODE_CBC, iv )
encrypted_text = base64.b64encode( iv + cipher.encrypt( str.encode(raw) ) )
return encrypted_text;
I'm encrypting a string in a web application using CryptoJS (v 2.3), and I need to decrypt it on the server in Python, so I'm using PyCrypto. I feel like I'm missing something because I can't can it working.
Here's the JS:
Crypto.AES.encrypt('1234567890123456', '1234567890123456',
{mode: new Crypto.mode.CBC(Crypto.pad.ZeroPadding)})
// output: "wRbCMWcWbDTmgXKCjQ3Pd//aRasZ4mQr57DgTfIvRYE="
The python:
from Crypto.Cipher import AES
import base64
decryptor = AES.new('1234567890123456', AES.MODE_CBC)
decryptor.decrypt(base64.b64decode("wRbCMWcWbDTmgXKCjQ3Pd//aRasZ4mQr57DgTfIvRYE="))
# output: '\xd0\xc2\x1ew\xbb\xf1\xf2\x9a\xb9\xb6\xdc\x15l\xe7\xf3\xfa\xed\xe4\xf5j\x826\xde(m\xdf\xdc_\x9e\xd3\xb1'
Here is a version with CryptoJS 3.1.2. Always beware of the following things (use the same in both languages):
Mode of operation (CBC in this case)
Padding (Zero Padding in this case; better use PKCS#7 padding)
Key (the same derivation function or clear key)
Encoding (same encoding for key, plaintext, ciphertext, ...)
IV (generated during encryption, passed for decryption)
If a string is passed as the key argument to the CryptoJS encrypt() function, the string is used to derive the actual key to be used for encryption. If you wish to use a key (valid sizes are 16, 24 and 32 byte), then you need to pass it as a WordArray.
The result of the CryptoJS encryption is an OpenSSL formatted ciphertext string. To get the actual ciphertext from it, you need to access the ciphertext property on it.
The IV must be random for each encryption so that it is semantically secure. That way attackers cannot say whether the same plaintext that was encrypted multiple times is actually the same plaintext when only looking at the ciphertext.
Below is an example that I have made.
JavaScript:
var key = CryptoJS.enc.Utf8.parse('1234567890123456'); // TODO change to something with more entropy
function encrypt(msgString, key) {
// msgString is expected to be Utf8 encoded
var iv = CryptoJS.lib.WordArray.random(16);
var encrypted = CryptoJS.AES.encrypt(msgString, key, {
iv: iv
});
return iv.concat(encrypted.ciphertext).toString(CryptoJS.enc.Base64);
}
function decrypt(ciphertextStr, key) {
var ciphertext = CryptoJS.enc.Base64.parse(ciphertextStr);
// split IV and ciphertext
var iv = ciphertext.clone();
iv.sigBytes = 16;
iv.clamp();
ciphertext.words.splice(0, 4); // delete 4 words = 16 bytes
ciphertext.sigBytes -= 16;
// decryption
var decrypted = CryptoJS.AES.decrypt({ciphertext: ciphertext}, key, {
iv: iv
});
return decrypted.toString(CryptoJS.enc.Utf8);
}
Python 2 code with pycrypto:
BLOCK_SIZE = 16
key = b"1234567890123456" # TODO change to something with more entropy
def pad(data):
length = BLOCK_SIZE - (len(data) % BLOCK_SIZE)
return data + chr(length)*length
def unpad(data):
return data[:-ord(data[-1])]
def encrypt(message, key):
IV = Random.new().read(BLOCK_SIZE)
aes = AES.new(key, AES.MODE_CBC, IV)
return base64.b64encode(IV + aes.encrypt(pad(message)))
def decrypt(encrypted, key):
encrypted = base64.b64decode(encrypted)
IV = encrypted[:BLOCK_SIZE]
aes = AES.new(key, AES.MODE_CBC, IV)
return unpad(aes.decrypt(encrypted[BLOCK_SIZE:]))
Warning: Keep in mind that both python2 and pycrypto are obsolete, so the code has to be adjusted to fit python3 and pycryptodome.
Other considerations:
It seems that you want to use a passphrase as a key. Passphrases are usually human readable, but keys are not. You can derive a key from a passphrase with functions such as PBKDF2, bcrypt or scrypt.
The code above is not fully secure, because it lacks authentication. Unauthenticated ciphertexts may lead to viable attacks and unnoticed data manipulation. Usually the an encrypt-then-MAC scheme is employed with a good MAC function such as HMAC-SHA256.
I had to port a Javascript implementation of AES encryption/decryption which was using crypto-js library, to Python3.
Basically, my approach was to run the debugger on the existing JS code and look at variables getting filled in each step. I was able to figure out the equivalent methods to do the same in python as well.
Here is how I ported it using pycryptodome library which has some useful features.
AES.js
var CryptoJS = require("crypto-js");
var Base64 = require("js-base64");
function decrypt(str, secret) {
try {
var _strkey = Base64.decode(secret);
var reb64 = CryptoJS.enc.Hex.parse(str);
var text = reb64.toString(CryptoJS.enc.Base64);
var Key = CryptoJS.enc.Base64.parse(_strkey.split(",")[1]); //secret key
var IV = CryptoJS.enc.Base64.parse(_strkey.split(",")[0]); //16 digit
var decryptedText = CryptoJS.AES.decrypt(text, Key, { keySize: 128 / 8, iv: IV, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7 });
return decryptedText.toString(CryptoJS.enc.Utf8); //binascii.unhexlify(decryptedText)
} catch (e) {
console.log("Error", e)
}
}
function encrypt(str, secret) {
str = Math.random().toString(36).substring(2, 10) + str;
var _strkey = Base64.decode(secret);
_strkey.split(",");
var text = CryptoJS.enc.Utf8.parse(str);
var Key = CryptoJS.enc.Base64.parse(_strkey.split(",")[1]); //secret key
var IV = CryptoJS.enc.Base64.parse(_strkey.split(",")[0]); //16 digit
var encryptedText = CryptoJS.AES.encrypt(text, Key, { keySize: 128 / 8, iv: IV, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7 });
var b64 = encryptedText.toString();
var e64 = CryptoJS.enc.Base64.parse(b64);
var eHex = e64.toLocaleString(CryptoJS.enc.Hex);
return eHex.toUpperCase();
}
const secret = "V1VWTVRFOVhJRk5WUWsxQlVrbE9SUT09LFRrOUNUMFJaSUZkSlRFd2dTMDVQVnc9PQ=="
const data = "THIS IS MY SECRET MESSAGE!"
encData = EncryptText2(data, secret)
decData = DecryptText2(encData, secret)
console.log("encryptedData", encData)
console.log("decryptedData", decData)
AESify.py
import string
import random
import base64
import binascii
from Crypto.Cipher import AES
from Crypto.Util.Padding import pad, unpad
class AESify:
def __init__(self, key=None, iv=None,secret = None, block_len=16, salt_len= 8):
self.key = key
self.iv = iv
self.salt_len = salt_len
self.block_len = block_len
self.mode = AES.MODE_CBC
if(secret):
self.useSecret(secret)
if(self.key is None and self.iv is None):
raise Exception("No key , IV pair or secret provided")
#staticmethod
def makeSecret(key, iv):
if(len(key) % 8 != 0):
raise Exception("Key length must be a mutliple of 8")
if(len(iv) % 8 != 0):
raise Exception("Initial vector must be a multiple of 8")
key64 = base64.b64encode(key.encode()).decode()
iv64 = base64.b64encode(iv.encode()).decode()
secret = iv64 + "," + key64
secret64 = base64.b64encode(secret.encode()).decode()
return secret64
def useSecret(self, secret):
iv64, key64 = base64.b64decode(secret).decode().split(",") # decode and convert to string
self.iv = base64.b64decode(iv64)
self.key = base64.b64decode(key64)
return self
def encrypt(self, text):
text = self.add_salt(text, self.salt_len)
cipher = AES.new(self.key, self.mode, self.iv)
text = cipher.encrypt(pad(text.encode('utf-8'), self.block_len))
return binascii.hexlify(text).decode()
def decrypt(self, data):
text = binascii.unhexlify(data) # UNHEX and convert the encrypted data to text
cipher = AES.new(self.key, self.mode, self.iv)
return unpad(cipher.decrypt(text), self.block_len).decode('utf-8')[self.salt_len:]
def add_salt(self, text, salt_len):
# pre-pad with random salt
salt = ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(salt_len))
text = salt + text
return text
main.py
from AESify import AESify
key , iv = "NOBODY WILL KNOW", "YELLOW SUBMARINE"
# contains IV and key
secret = AESify.makeSecret(key, iv)
aes = AESify(secret= secret, block_len=16, salt_len=4)
msg = "THIS IS MY SECRET MESSAGE"
encrypted = aes.encrypt(msg)
decrypted = aes.decrypt(encrypted)
print(f"{secret=}")
print(f"{encrypted=}")
print(f"{decrypted=}")
Note : salt , iv , padding should be same in js and python
generate salt and iv value and convert it into a byte string uisng CryptoJS.enc.Utf8.parse()
js file
var encrypted = CryptoJS.AES.encrypt(JSON.stringify(json_data), CryptoJS.enc.Utf8.parse(data['salt']) , { iv: CryptoJS.enc.Utf8.parse(data['iv']) , mode: CryptoJS.mode.CBC , padding: CryptoJS.pad.Pkcs7});
en_data = encrypted.ciphertext.toString(CryptoJS.enc.Base64)
send this encrypted data to the python file
python file
from Crypto.Util.Padding import pad, unpad
ct = request.POST['encrypted_data']
data = base64.b64decode(ct)
cipher1 = AES.new(salt, AES.MODE_CBC, iv)
pt = unpad(cipher2.decrypt(data), 16)
data = json.loads(pt.decode('utf-8'))
pad and upad in pycrypto by default uses pkcs#7
salt and iv value should in byte string