CODEWITHSUNDEEP
javascriptandroidencryptionaescryptojs
Tangela
Tangela

Reputation: 161

Password-based AES encryption on Android and decryption with CryptoJS

On Android I have no problem encrypting a message and getting the iv.

String Test = "Lorem ipsum dolor sit amet, ...";
String password = "test";

KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(password.getBytes("UTF8"));
kgen.init(256, sr);
SecretKey skey = kgen.generateKey();

Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
SecretKeySpec skeySpec = new SecretKeySpec(skey.getEncoded(), "AES");
c.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] decrypted = c.doFinal(Test.getBytes());
decrypted = Base64.encodeBase64(decrypted);
byte[] iv = Base64.encodeBase64(c.getIV());
Log.d("encryptString", new String(decrypted));
Log.d("encryptString iv", new String(iv));

Output example:

encryptString: 2NVoJzMkPphwUJc2h/4LfsmAwyJlejbWKGLG2ACNbaI=
encryptString iv: YX5SF+cFwzv1I4OiGrJk3A==

When I move over to the JavaScript side I first convert the base64 encoding to bytes. Then I run it through the CryptoJS AES Decrypt function.

var decrypt = CryptoJS.enc.Base64.parse("2NVoJzMkPphwUJc2h/4LfsmAwyJlejbWKGLG2ACNbaI=");
var iv = CryptoJS.enc.Base64.parse("YX5SF+cFwzv1I4OiGrJk3A==");
var password = "test";

var encrypted = CryptoJS.AES.decrypt(decrypt.toString(), password, {
    iv: iv,
    mode: CryptoJS.mode.CBC,
    padding: CryptoJS.pad.Pkcs7
});

Output is always empty. Is there something else I am missing on Android that I also need to pass to CryptoJS?

Upvotes: 0

Views: 1823

Answers (1)

Tangela
Tangela

Reputation: 161

Found the problem and it was not an padding issue.

As other people have stated it have to do with the fact I was using SecureRandom.getInstance("SHA1PRNG").

I corrected the problem in my code was generating a key with PBEKeySpec on Android and PBKDF2 on CryptoJS. Then just following the same steps:

String Test = "Lorem ipsum dolor sit amet, ...";
String password = "test";

byte[] salt = new String("12345678").getBytes("Utf8");
int iterationCount = 2048;
int keyStrength = 256;

SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
KeySpec spec = new PBEKeySpec(password.toCharArray(), salt, iterationCount, keyStrength);
SecretKey tmp = factory.generateSecret(spec);

Log.d("encryptString Key: ", new String(Base64.encodeBase64(tmp.getEncoded())));

Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.ENCRYPT_MODE, tmp);
byte[] decrypted = c.doFinal(Test.getBytes());
decrypted = Base64.encodeBase64(decrypted);
byte[] iv = c.getIV();

Log.d("encryptString: ", new String(decrypted));
Log.d("encryptString iv:", new String(Base64.encodeBase64(iv)));

Example output from run code on Android:

encryptString Key:: ueTU6u4PXbm86zy+UtlQfeh55xZorA58W3fKKBypheM=
encryptString:: ii8UNoi4xG1zGC8RyzHKu6JMkxixkK7LTPxGMaCHGNk=
encryptString iv:: nwy2VHctPnXOd/rahPFiWg==

Now we generate the same PBKDF2 key in a JavaScript and input the output above into our sample code below:

var salt = CryptoJS.enc.Utf8.parse("12345678");
var password = "test";
var keyBits = CryptoJS.PBKDF2(password, salt, {
  hasher: CryptoJS.algo.SHA1,
  keySize: 8,
  iterations: 2048
});

var iv = CryptoJS.enc.Base64.parse("nwy2VHctPnXOd/rahPFiWg==");
var message = CryptoJS.enc.Base64.parse("ii8UNoi4xG1zGC8RyzHKu6JMkxixkK7LTPxGMaCHGNk=");

var encrypted = CryptoJS.AES.decrypt("ii8UNoi4xG1zGC8RyzHKu6JMkxixkK7LTPxGMaCHGNk=", keyBits, {
  iv: iv,
  padding: CryptoJS.pad.Pkcs7,
  mode: CryptoJS.mode.CBC
});

console.log(encrypted.toString(CryptoJS.enc.Utf8));
<!doctype html>

<html>

<head>
</head>

<body>
  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/crypto-js.min.js"></script>
  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/pbkdf2.min.js"></script>
  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/aes.min.js"></script>
</body>

</html>

Output in JavaScript:

"Lorem ipsum dolor sit amet, ..."

Upvotes: 4

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