ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: The Most Confused Concepts in Engineering

Think back to the last time when you were searching something on Google.

If you notice your browser bar, you may see something like this.

If we look carefully, we can see that the spaces are actually replaced by person 20, and question mark is replaced by person 3f.

The browser somehow transformed our query into something different.

Why?

Because the URLs are allowed to have only a limited number of characters, and in that character set, characters like space are not valid.

but it still needs to be sent, and therefore it is converted into something that belongs to the allowed character set.

This type of transformation of data from one form to another, for the purpose of storage or transmission, is called encoding.

And similar to this, the data can be encoded to other forms as well.

For example, the text hello can be converted into many different forms, for example binary, hexadecimal, or base64.

The encoding is not only limited to transmitting data, but has other uses as well.

For example, if you work on the front-end with CSS, you might have seen the color codes which have the RGB values.

Those values are usually written in hexadecimal for its compact nature.

In decimal, the same value would look like this.

Similarly, in HTML, you may have seen the image stack to add images to your page, which refer to the URL where the image resides.

While this is fine for large images, The lighter images can be directly embedded in the Base64 format via HTML or CSS to save a network call.

The key point to understand here is that encoding is reversible.

For example, anyone who sees person 20 can decode it back to a space.

It's about data representation, not security.

And speaking of security, let's talk a bit about hashing.

Whenever you create an account online, your password is never stored in plain text.

Instead, it's converted into a fixed-length string of characters, which could look like this.

From this string alone, it is impossible to construct the original password again, and this type of transformation is possible by a process called hashing.

Hashing is a process where you convert data into another irreversible form by the use of a hashing algorithm, which does some complex math behind the scenes to achieve this.

So when you login, the password that you enter is hashed again and compared with the hash that exists in the system.

If they are same, the login is successful.

Hashing is defined by three main things.

First, that it is one way.

You can't reverse a hash to retrieve the original input.

Second, it is deterministic.

The same input always produces the same hash.

And third, is that it is always of fixed length.

So, no matter how long your password is, the hash always will be of the same size.

Hashing is not only used in passwords, but it has other applications as well.

For example, in file downloads.

If the downloaded file is corrupt, its hash would be different from the original file.

Whereas if the downloaded file is intact, its hash would be the same as original file.

If you're intrigued by hashing, check out my deep dive video on what is hashing, to learn about different hashing algorithms and hash collisions.

Now, what if you need that one-way transformation to be two-way, but only for some selected people or systems?

That's where encryption comes in.

Imagine that you have a top-secret document on your computer.

Anyone with access to your machine can open and read it.

Encryption provides a way to transform your document or data into a form

that can only be reversed by the use of a key.

So whoever holds the key can access the data.

If someone tries to open it without the key, they'll only see gibberish.

Let's take a simple example of encryption, one that dates back over 2000 years.

Julius Caesar used a basic encryption technique to protect messages of military importance.

It's now famously known as Caesar's cipher, or the shift cipher.

The idea?

Shift each letter of the message by a fixed number of positions in the alphabet.

say 3.

So if we take the word hello and shift each letter by 3, H becomes K, E becomes H,

L becomes O, the next L also becomes O, and O becomes R.

That gives us KHOOR.

To anyone who intercepts this message without knowing the shift, it looks like gibberish.

But if the recipient knows that each letter was shifted by 3, they can just reverse the shift and decrypt the message back to hello.

This kind of encryption is laughably easy to crack today, especially with modern computers.

But it beautifully illustrates the core idea.

The message is only readable to someone who has the key.

Modern encryption is, let's just say, a bit more advanced.

Instead of the letter shifts, we now use complex mathematical algorithms that are designed to be unbreakable by brute force, at least with current computers.

Quantum computing might change that, but that's a topic for another video.

Take WhatsApp, for example.

Every message that you send is encrypted on your device before it even leaves your phone.

If someone tries to snoop on the network, all they see is garbled nonsense.

Only the person that you are messaging with the matching decryption key can turn that noise back into actual words.

That's encryption, locking your data in such a way that only the right key can unlock it.

To put it all together, encoding is like translating data into another format so computers can store or transmit it properly.

It's not about secrecy, it's about structure and readability.

And yes, it is completely reversible.

Some examples are UTF-8, binary, hexadecimal, and base64.

Hashing takes your data and runs it through a special formula to create a unique, fixed-length code.

This code doesn't reveal the original data, and you cannot convert it back.

That's why it's perfect for safely storing passwords or checking if a file has been tampered with.

If the data changes, the hash changes too.

Encryption is about confidentiality.

It transforms your data into something unreadable, but only temporarily.

Because unlike hashing, encryption is reversible if and only if you have the right key.

That's how secure messaging apps like WhatsApp protect your conversations even from their own servers.

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ฝึกพูดภาษาอังกฤษด้วยเทคนิค Shadowing จากวิดีโอ: The Most Confused Concepts in Engineering

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