JavaScript string encryption and decryption?

Question

I'm interested in building a small app for personal use that will encrypt and decrypt information on the client side using JavaScript. The encrypted information will be stored in a database on a server, but never the decrypted version.

It doesn't have to be super duper secure, but I would like to use a currently unbroken algorithm.

Ideally I'd be able to do something like

var gibberish = encrypt(string, salt, key);

to generate the encoded string, and something like

var sensical = decrypt(gibberish, key);

to decode it later.

So far I've seen this: http://bitwiseshiftleft.github.io/sjcl/

Any other libraries I should look at?

Answer 1

 var encrypted = CryptoJS.AES.encrypt("Message", "Secret Passphrase");
//U2FsdGVkX18ZUVvShFSES21qHsQEqZXMxQ9zgHy+bu0=

var decrypted = CryptoJS.AES.decrypt(encrypted, "Secret Passphrase");
//4d657373616765


document.getElementById("demo1").innerHTML = encrypted;
document.getElementById("demo2").innerHTML = decrypted;
document.getElementById("demo3").innerHTML = decrypted.toString(CryptoJS.enc.Utf8);

Full working sample actually is:

    <script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.2/rollups/aes.js" integrity="sha256-/H4YS+7aYb9kJ5OKhFYPUjSJdrtV6AeyJOtTkw6X72o=" crossorigin="anonymous"></script>

<br><br>
<label>encrypted</label>
<div id="demo1"></div>
<br>

<label>decrypted</label>
<div id="demo2"></div>

<br>
<label>Actual Message</label>
<div id="demo3"></div>

Answer 2

How about CryptoJS?

It's a solid crypto library, with a lot of functionality. It implements hashers, HMAC, PBKDF2 and ciphers. In this case ciphers is what you need. Check out the quick-start quide on the project's homepage.

You could do something like with the AES:

<script src="http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/aes.js"></script>

<script>
    var encryptedAES = CryptoJS.AES.encrypt("Message", "My Secret Passphrase");
    var decryptedBytes = CryptoJS.AES.decrypt(encryptedAES, "My Secret Passphrase");
    var plaintext = decryptedBytes.toString(CryptoJS.enc.Utf8);
</script>

As for security, at the moment of my writing AES algorithm is thought to be unbroken

Edit :

Seems online URL is down & you can use the downloaded files for encryption from below given link & place the respective files in your root folder of the application.

https://code.google.com/archive/p/crypto-js/downloads

or used other CDN like https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.2/components/aes-min.js

Answer 3

I created an insecure but simple text cipher/decipher utility. No dependencies with any external library.

These are the functions:

const cipher = salt => {
    const textToChars = text => text.split('').map(c => c.charCodeAt(0));
    const byteHex = n => ("0" + Number(n).toString(16)).substr(-2);
    const applySaltToChar = code => textToChars(salt).reduce((a,b) => a ^ b, code);

    return text => text.split('')
      .map(textToChars)
      .map(applySaltToChar)
      .map(byteHex)
      .join('');
}
    
const decipher = salt => {
    const textToChars = text => text.split('').map(c => c.charCodeAt(0));
    const applySaltToChar = code => textToChars(salt).reduce((a,b) => a ^ b, code);
    return encoded => encoded.match(/.{1,2}/g)
      .map(hex => parseInt(hex, 16))
      .map(applySaltToChar)
      .map(charCode => String.fromCharCode(charCode))
      .join('');
}

// To create a cipher
const myCipher = cipher('mySecretSalt')

//Then cipher any text:
console.log(myCipher('the secret string'))

//To decipher, you need to create a decipher and use it:
const myDecipher = decipher('mySecretSalt')
console.log(myDecipher("7c606d287b6d6b7a6d7c287b7c7a61666f"))

Answer 4

This code is based on @Jorgeblom's answer above.

---

@Jorgeblom my man, that's fantastic small crypto lib :D I touch it a bit because I didn't like that I have to assign the salt and to call it again but in general, for my needs is absolutely perfect.

const crypt = (salt, text) => {
  const textToChars = (text) => text.split("").map((c) => c.charCodeAt(0));
  const byteHex = (n) => ("0" + Number(n).toString(16)).substr(-2);
  const applySaltToChar = (code) => textToChars(salt).reduce((a, b) => a ^ b, code);

  return text
    .split("")
    .map(textToChars)
    .map(applySaltToChar)
    .map(byteHex)
    .join("");
};

const decrypt = (salt, encoded) => {
  const textToChars = (text) => text.split("").map((c) => c.charCodeAt(0));
  const applySaltToChar = (code) => textToChars(salt).reduce((a, b) => a ^ b, code);
  return encoded
    .match(/.{1,2}/g)
    .map((hex) => parseInt(hex, 16))
    .map(applySaltToChar)
    .map((charCode) => String.fromCharCode(charCode))
    .join("");
};

And you use it

// encrypting
const encrypted_text = crypt("salt", "Hello"); // -> 426f666665

// decrypting
const decrypted_string = decrypt("salt", "426f666665"); // -> Hello