When attempting to decrypt with a password using CryptoJS, AES decryption returns an empty result

Question

When attempting to decrypt with a password using CryptoJS, AES decryption returns an empty result

Example

The code snippet below is what I am currently using:

<script src="http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/aes.js"></script>
<div id="decrypted">Please wait...</div>
Insert new note:<input type="text" id="new_note"><input type="button" id="enc_button" value="Save">
<script>
    var password = "testpassword";
    var encrypted_text = localStorage.getItem("encrypted");
    var rawData = atob(encrypted_text);
    var iv = rawData.substring(0,16);
    var crypttext = rawData.substring(16);
    var plaintextArray = CryptoJS.AES.decrypt(
      { ciphertext: CryptoJS.enc.Latin1.parse(crypttext) },
      CryptoJS.enc.Hex.parse(password),
      { iv: CryptoJS.enc.Latin1.parse(iv) }
    );
    var decrypted = CryptoJS.enc.Latin1.stringify(plaintextArray);
    document.getElementById("decrypted").innerHTML = decrypted;
    document.getElementById("enc_button").onclick = function(){
    var text = document.getElementById("new_note").value;
    var encrypted = CryptoJS.AES.encrypt(text, password);
    localStorage.setItem("encrypted",encrypted);
    }
</script>

Intended Functionality

The goal is to encrypt a string with AES using CryptoJS and then decrypt the saved encrypted text from local storage to display the result in a div.

Current Issue

Although the string appears to be encrypted successfully, the variable decrypt remains empty. No errors are being logged in the Chrome console.

Inquiry

How can I ensure successful encryption and decryption of my text?

javascript encryption cryptography cryptojs

Answer 1

Answer №1

CryptoJS offers two variations of encryption and decryption methods.

When utilizing

var encrypted = CryptoJS.AES.encrypt(text, password);

you are engaging in password-based encryption as opposed to traditional key/IV-based encryption. Essentially, this method involves running the password and a randomly generated salt through an MD5 invocation to generate the key and IV for encryption purposes. The resulting encrypted object retains the salt used to derive the key and IV.

If you convert encrypted into a string (e.g., storing it in localStorage), it transforms into an OpenSSL compatible string encoding that includes the salt. To decrypt it, there is no need to handle the key, IV, or salt manually; CryptoJS handles this process automatically:

var decrypted = CryptoJS.AES.decrypt(encrypted, password);

Note that decrypted is represented as a WordArray object, which converts to Hex by default when turned into a string. To specify another encoding like UTF-8, you must define it explicitly.

If decryption fails due to factors like an incorrect key, ciphertext, or encoding, CryptoJS typically returns a blank value instead of throwing custom error messages. The library assumes users understand the intricacies of their actions.

Here is the full code snippet:

var password = "testpassword";

document.getElementById("enc_button").onclick = function(){
  var text = document.getElementById("new_note").value;
  
  var encrypted = CryptoJS.AES.encrypt(text, password);
  encrypted = encrypted.toString();
  
  var decrypted = CryptoJS.AES.decrypt(encrypted, password);
  decrypted = decrypted.toString(CryptoJS.enc.Utf8)
  
  document.getElementById("decrypted").innerHTML = decrypted;
}

<script src="https://cdn.rawgit.com/CryptoStore/crypto-js/3.1.2/build/rollups/aes.js"></script>
<div id="decrypted">Please wait...</div>
Insert new note:<input type="text" id="new_note"><input type="button" id="enc_button" value="Encrypt & Decrypt">

Answer 2

CryptoJS offers two variations of encryption and decryption methods.

When utilizing

var encrypted = CryptoJS.AES.encrypt(text, password);

you are engaging in password-based encryption as opposed to traditional key/IV-based encryption. Essentially, this method involves running the password and a randomly generated salt through an MD5 invocation to generate the key and IV for encryption purposes. The resulting encrypted object retains the salt used to derive the key and IV.

If you convert encrypted into a string (e.g., storing it in localStorage), it transforms into an OpenSSL compatible string encoding that includes the salt. To decrypt it, there is no need to handle the key, IV, or salt manually; CryptoJS handles this process automatically:

var decrypted = CryptoJS.AES.decrypt(encrypted, password);

Note that decrypted is represented as a WordArray object, which converts to Hex by default when turned into a string. To specify another encoding like UTF-8, you must define it explicitly.

If decryption fails due to factors like an incorrect key, ciphertext, or encoding, CryptoJS typically returns a blank value instead of throwing custom error messages. The library assumes users understand the intricacies of their actions.

Here is the full code snippet:

var password = "testpassword";

document.getElementById("enc_button").onclick = function(){
  var text = document.getElementById("new_note").value;
  
  var encrypted = CryptoJS.AES.encrypt(text, password);
  encrypted = encrypted.toString();
  
  var decrypted = CryptoJS.AES.decrypt(encrypted, password);
  decrypted = decrypted.toString(CryptoJS.enc.Utf8)
  
  document.getElementById("decrypted").innerHTML = decrypted;
}

<script src="https://cdn.rawgit.com/CryptoStore/crypto-js/3.1.2/build/rollups/aes.js"></script>
<div id="decrypted">Please wait...</div>
Insert new note:<input type="text" id="new_note"><input type="button" id="enc_button" value="Encrypt & Decrypt">

Answer 3

Answer №2

While trying to troubleshoot your code, I discovered that the script was placed in a try-catch block and it seems like document.getElementById is returning undefined. This is likely due to the method being called before the element is created. To resolve this issue, follow these steps:

Head:

var password = "securepassword";
var encrypted_text = localStorage.getItem("encrypted_data");
var rawData = atob(encrypted_text);
var iv = rawData.substring(0, 16);
var crypttext = rawData.substring(16);
var plaintextArray = CryptoJS.AES.decrypt(
    { ciphertext: CryptoJS.enc.Latin1.parse(crypttext) },
    CryptoJS.enc.Hex.parse(password),
    { iv: CryptoJS.enc.Latin1.parse(iv) }
);
var decryptedData = CryptoJS.enc.Latin1.stringify(plaintextArray);

function setComponents() {
    try {
        document.getElementById("decrypted_content").innerHTML = decryptedData;
        document.getElementById("encryption_button").onclick = function(){
            var inputText = document.getElementById("new_note_input").value;
            var encryptedMessage = CryptoJS.AES.encrypt(inputText, password);
            localStorage.setItem("encrypted_data", encryptedMessage);
            alert(encryptedMessage);
        };
    } catch(error) {
        alert(error);
    }
}

Body:

<body onload="setComponents()">
<div id="decrypted_content">Please wait...</div>
Insert new note:<input type="text" id="new_note_input"/><input type="button" id="encryption_button" value="Save"/>
</body>

Answer 4

While trying to troubleshoot your code, I discovered that the script was placed in a try-catch block and it seems like document.getElementById is returning undefined. This is likely due to the method being called before the element is created. To resolve this issue, follow these steps:

Head:

var password = "securepassword";
var encrypted_text = localStorage.getItem("encrypted_data");
var rawData = atob(encrypted_text);
var iv = rawData.substring(0, 16);
var crypttext = rawData.substring(16);
var plaintextArray = CryptoJS.AES.decrypt(
    { ciphertext: CryptoJS.enc.Latin1.parse(crypttext) },
    CryptoJS.enc.Hex.parse(password),
    { iv: CryptoJS.enc.Latin1.parse(iv) }
);
var decryptedData = CryptoJS.enc.Latin1.stringify(plaintextArray);

function setComponents() {
    try {
        document.getElementById("decrypted_content").innerHTML = decryptedData;
        document.getElementById("encryption_button").onclick = function(){
            var inputText = document.getElementById("new_note_input").value;
            var encryptedMessage = CryptoJS.AES.encrypt(inputText, password);
            localStorage.setItem("encrypted_data", encryptedMessage);
            alert(encryptedMessage);
        };
    } catch(error) {
        alert(error);
    }
}

Body:

<body onload="setComponents()">
<div id="decrypted_content">Please wait...</div>
Insert new note:<input type="text" id="new_note_input"/><input type="button" id="encryption_button" value="Save"/>
</body>

Answer 5

Answer №3

If you're struggling with API development, double check the contents of your request body to ensure that all object properties are correctly named! It might seem simple, but it can save you hours of frustration.

Answer 6

If you're struggling with API development, double check the contents of your request body to ensure that all object properties are correctly named! It might seem simple, but it can save you hours of frustration.

Answer 7

Answer №4

If you want to see examples, just take a look at the source code.
The simplest way to generate key, iv, and salt from a passphrase is using CryptoJS.AES.encrypt("attack at dawn!","passphrase")
You can also set parameters upfront like this:

CryptoJS.algo.AES.keySize=32
CryptoJS.algo.AES.blockSize=8
CryptoJS.algo.AES.ivSize=16
CryptoJS.algo.EvpKDF.cfg.iterations=100
CryptoJS.algo.EvpKDF.cfg.keySize=32

and so on.

Answer 8

If you want to see examples, just take a look at the source code.
The simplest way to generate key, iv, and salt from a passphrase is using CryptoJS.AES.encrypt("attack at dawn!","passphrase")
You can also set parameters upfront like this:

CryptoJS.algo.AES.keySize=32
CryptoJS.algo.AES.blockSize=8
CryptoJS.algo.AES.ivSize=16
CryptoJS.algo.EvpKDF.cfg.iterations=100
CryptoJS.algo.EvpKDF.cfg.keySize=32

and so on.

When attempting to decrypt with a password using CryptoJS, AES decryption returns an empty result

Example

Intended Functionality

Current Issue

Inquiry

Answer №1

Answer №2

Answer №3

Answer №4

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