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Removing a class from an HTML-Element with JavaScript is easy enough. You could use jQuery for it by calling

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$(node).removeClass(className);

or, just as simple, go vanilla with:

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var node = document.getElementById(id);
node.classList.remove(className);

But what if you wanted to remove all classes starting with a prefix? Assume we have a DOM-Node like this:

This post is part of a series about symmetric encryption with AES-256 in PHP.

In this last part of our series we’re going to learn how to decrypt files we previously encrypted using our Crypto class.

After encrypting text in the previous post, here’s how you get your plaintext back.

The code

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decrypt: function(encryptedString, secret) {
	// Separate payload from potential hmac
	var separated = encryptedString.trim().split(":");

	// Extract HMAC if signed
	var hmac = (separated[1]) ? separated[1] : "";

	// Decode
	var raw = this.base64UrlDecode(separated[0]);

	// Extract IV
	var iv = CryptoJS.lib.WordArray.create(raw.words.slice(0, this.blockSize / 32));

	// Extract Salt
	var salt = CryptoJS.lib.WordArray.create(raw.words.slice(this.blockSize / 32, this.blockSize / 32 + this.blockSize / 32));

	// Extract ciphertext
	var ciphertext = CryptoJS.lib.WordArray.create(raw.words.slice(this.blockSize / 32 + this.blockSize / 32));

	// Generate key
	var key = this.generateKey(secret, salt);

	if (hmac && !(this.sign(separated[0], key) == hmac)) {
		return null;
	}

	// Init cipher
	var cipherParams = CryptoJS.lib.CipherParams.create({ciphertext: ciphertext});

	// Decrypt
	var plaintextArray = CryptoJS.AES.decrypt(
	  cipherParams,
	  key,
	  {iv: iv}
	);

	// Encode
	return CryptoJS.enc.Utf8.stringify(plaintextArray);
},

Decoding

After checking for a signature and saving it for later if there is one, we decode the Base64-encoded string back to raw.

This post is part of a series about symmetric encryption with AES-256 in PHP.

After encrypting text in the previous post, we now want to be able to decrypt that as well.

This post is the first part of a series about symmetric encryption with AES-256 in PHP.

There are plenty usecases for having encryption in your application, but be aware of the golden rule of cryptography: If you don’t know what you’re doing, don’t do it! Simply labeling your application “AES256-encrypted” doesn’t necessarily mean, it’s secure because you may have intruduced attack vectors in your implementation. Still, it’s fun to play around with it to understand what’s required to encrypt a text or file.

I’m sure all of you know Quick Response Codes (or QR-Codes for short). They’re everywhere and a great way to encode information that’s hard to read and/or remember for humans in a way machines can process. There are plenty of online services that will generate QR-codes for us. But what if we wanted to be able to do this ourselves to use such a feature in our own application?

When searching the web for ways to center a DIV I found a ton of suggestions. Many kind of solved one problem but at the same time introduced others, some made the code unreadable and others straight up didn’t work at all.

Eventually I got frustrated and decided to tinker around for a couple hours myself on a problem that seems like there should be a native solution for it - but there isn’t.

Backups are crucial. I hope we agree on that one. When I started this website, one of the major things that occupied my mind was “How do I make sure, all the work I put into this project is safe from an attack, system failure or me accidentaly clicking ‘Delete All! Now!’?”