Unable to decrypt message using Crypto-Js

Question

I am new to encryption. What I am trying to do is decrypt a cipher text using javascript library, CryptoJS. This code example works fine. The encryption part returns ciphertext "ae06b481cecfa67c98c125" (which is right) while decrypting the same object returns the original string "Hello World".

 var key = CryptoJS.enc.Latin1.parse("bad8deadcafef00d");
 var iv = CryptoJS.enc.Latin1.parse("bad8deadcafef00d");
 var encrypted = CryptoJS.AES.encrypt("Hello World", key, {iv: iv, mode: CryptoJS.mode.CTR, padding: CryptoJS.pad.NoPadding });
 alert(encrypted.ciphertext);

 var decryptedData = CryptoJS.AES.decrypt(encrypted, key, {iv: iv, mode: CryptoJS.mode.CTR, padding: CryptoJS.pad.NoPadding });
 originalData = decryptedData.toString(CryptoJS.enc.Utf8);
 alert(originalData);

Well this part works fine but when I try this chunk of code by passing the cipher text as a string independently, I don't get the decrypted message.

var key = CryptoJS.enc.Latin1.parse("bad8deadcafef00d");
var iv = CryptoJS.enc.Latin1.parse("bad8deadcafef00d");
var ciphertext = "ae06b481cecfa67c98c125";
// raw = CryptoJS.enc.Base64.parse(cipher);
var decryptedData = CryptoJS.AES.decrypt(ciphertext, key, {iv: iv, mode: CryptoJS.mode.CTR, padding: CryptoJS.pad.NoPadding });
originalData = decryptedData.toString(CryptoJS.enc.Utf8);
alert(originalData);
console.log(originalData);

Can somebody please point out why?

I have the following libraries included in the html file.

<script src="js/rollups/aes.js"></script>
<script src="js/components/mode-ctr.js"></script>
<script src="js/components/pad-nopadding.js"></script>

Answer 1

CryptoJS.AES.decrypt expects either a CipherParams object or an OpenSSL-formatted string. If the passed key is a string then the OpenSSL-formatted string is expected and otherwise the CipherParams object.

Since your key is not a string, you need this:

var decryptedData = CryptoJS.AES.decrypt({
    ciphertext: CryptoJS.enc.Hex.parse("ae06b481cecfa67c98c125")
}, key, {
    iv: iv, 
    mode: CryptoJS.mode.CTR, 
    padding: CryptoJS.pad.NoPadding
});

If the key is a string, then it isn't actually a key, but assumed to be a password and a key will be derived from that password with a random 8 byte salt. This would be comparable to OpenSSL's EVP_BytesToKey function.