What is AES encryption and how does it work?

AES (Advanced Encryption Standard) is an encryption method used to protect data on the internet.
AES is one of the best encryption protocols available today, offering the perfect combination of speed and security, allowing you to enjoy your everyday online activities seamlessly.

Its benefits make it no surprise that AES has become the industry standard for encryption.
In this article, we describe the origins, uses and potential threats of AES. In addition, you will learn how AES encryption works and we will explain each step of the encryption process step by step.

Why do we need the AES encryption algorithm?

When the standard data encryption algorithm known as the DES algorithm was developed and standardised, it made sense for this generation of computers. As the table below shows, modern computer standards over the years have made the DES algorithm easier and faster to decrypt.
The demand for stronger algorithms, larger key sizes and stronger encryptions has resulted in stronger encryptions being cracked. Triple DES was created to solve this problem, but did not become common because of its relatively low speed. Therefore, the advanced encryption standard was created to overcome this shortcoming.

The decryption process

Decrypting AES ciphertext is the reverse of the encryption process. Each round consists of four steps in reverse order.

  • Adding a keyboard
  • Shuffle columns
  • Moving columns
  • Byte exchange

Because each round is executed in reverse order, the encryption and decryption algorithms must be implemented separately, unlike the Feistel cipher, which is very close.

What is 128-bit AES encryption?

128-bit AES encryption is the encryption of data in plaintext using a 128-bit AES key. 128-bit AES encryption consists of 10 rounds of turning plaintext into ciphertext and is approved by the National Security Agency (NSA) to protect sensitive, but not top secret, government information.
The 128-bit AES encryption also refers to the fixed block size of the general AES encryption algorithm; the length of the AES key can vary between 128, 192 or 256 bits, but the block size of AES encrypted data is always 128 bits.

How is the AES encryption algorithm used for secure file transfer?

As mentioned earlier, AES is suitable for secure file transfer protocols such as FTPS, HTTPS, SFTP, AS2, WebDAVS and OFTP, but what exactly does it do?

Because symmetric and asymmetric encryption algorithms have their advantages, modern secure file transfer protocols often use a combination of both. Asymmetric-key encryption algorithms are similar to public-key encryption algorithms in their ability to distribute keys and are used to encrypt session keys used in symmetric-key encryption.

Symmetric-key encryption, such as AES, is suitable for encrypting real data (and commands) because it requires fewer resources and is faster than asymmetric-key encryption. For a more detailed explanation.
The figure below shows a simplified encryption process for a typical secure file transfer using SSL/TLS (HTTPS, FTPS, WebDAVS) or SSH (SFTP). In step 3, AES encryption is used.