Advanced Encryption Standard: AES Encryption Algorithm Guide

This tutorial provides a complete comprehensive understanding of the Advanced Encryption Standard AES with the help of some figures and examples:

In the world of electronic communication and technology, every process revolves around sending and receiving data and information through machines.

To receive and send sensitive data, personal information, and sensitive data related to the military operation, national security, etc. there should be some secure means of communication.

Here comes a picture of the encryption and decryption process. The Advanced Encryption Standard AES is the most widely used encryption method for securely encrypting data and processing further by using a secure connection.

Here we will discuss the process of AES encryption and decryption in short with the help of some figures and examples.

We have also answered some frequently asked queries regarding this topic.

What is AES Encryption

Advanced Encryption Standard

The Advanced Encryption Standard (AES) Encryption is explicit for the encryption of electronic information, and it was set up with the assistance of the U.S. (NIST) National Institute of Standards and Technology in 2001.

AES is based on the Rijndael methodology of encryption using a block cipher. Rijndael is a group of codes with various keys and square blocks. For AES, NIST named three individuals from the Rijndael family, each with a square size of 128 pieces. The three different key lengths: 128, 192, and 256 are used for encryption.

It is carried out in the programming and synthesis of sensitive and complex data to encode information. It is exceptionally beneficial for government PC security, network safety, and electronic information assurance.

Operations Advanced Encryption Standard (AES)

AES is called a ”supernumerary–transformation network. It contains a progression of connected tasks, which are inclusive of switching some inputs by explicit output (transformation) and others include interchanging bits among each other, which is also known as permutation.

AES executes the various computation processes on bytes than that bits. Thus, the 128 bits plaintext structure is treated as 16 bytes. This is further arranged in the form of a matrix for processing of bytes information with four columns and four rows structure.

The AES uses a variable number of rounds and its size depends on the encryption key length. For example, it utilizes 10 rounds for 128-digit keys and 14 rounds for 256-bit keys. Each time, the number of rounds used can be varied which is calibrated by the original AES key.

key structure

AES Encryption Key Structure:

AES encryption key structure

Encryption Process

The encryption process consists of various steps. AES deliberates every 16-byte block as 4-byte * 4-byte rows and column matrix format.

Now each round contains 4 sub-steps to conclude the process out of which the subbytes are used to perform the substitution and the shift rows, and mix columns to execute the permutation steps. If it is taking the last round, then the mixed columns round is not been performed.

The matrix arrangement is as follows:

encryption matrix

Let’s start one by one:

#1) Sub Bytes: At the initial level, the 16 bytes input is as plain text. The S-box, which is also known as the substitution box, is used to substitute each byte with a sub-byte by looking up into the S-box to convert the plain text into the form of the matrix. The S-box uses the 8-bit array.

The S-box is the combination of inverse functions over 2^8 in association with the invertible transformation.

#2) ShiftRows: It works on the rows of the matrix. Now each of the bytes of the second row is shifted to its left by one place. Similarly, in the third row, each byte is shifted to its left by two places. Each of the bytes in the fourth row is shifted to its left by three places and so on. Thus, it repeatedly shifts the bytes of the matrix in every row by a specific offset value.

Refer to the example below:

shift rows method of encryption

#3) MixColumns: In the Mixcolumns operation, the four bytes input of the column is converted into an entirely different four bytes output by performing some mathematical operations. This operation is not applied to the last round of the matrix.

This mathematical operation is a combination of multiplication and addition of the input values. In the mathematical expressions, each column is considered a polynomial over the 2^8, which is further multiplied by a fixed polynomial expression. The addition is further performed by using the XOR function on the output of the multiplied values.

The operation is shown below:

Mix columns method encryption

Add Round Key: The 16 bytes matrix is converted into 128 bits format to perform the round key step. For every round, a subkey is derived from the main round key by using Rijndael’s key methodology. Now the XOR function is performed between the 128 bits of the matrix and the 128 bits of the subkey to obtain the desired output.

The process is shown in the diagram below. It is followed until all the data to be encrypted is not processed.

Encryption Process:

encryption process

Decryption Process

The decryption method is the same as the encryption process, but in the opposite sequence. Each round consists of four steps performed in inverse order. First, the add round key process will be implemented.

Then inverse mix columns and shift rows steps will be executed. At last, the byte substitution will take place in which the inverse Sub Bytes process is followed to perform the inverse transformation and then the inverse multiplication. The output will be the plain ciphertext.

Where is the AES Algorithm Encryption Used

National security agencies in many countries inclusive of India recommend using the 256-bit AES encryption algorithm for saving and sending crucial and sensitive data over secure communication channels. The military and other government agencies, for example, finance ministry, also use 256-bit AES encryption for data storage on day to day basis.

AES algorithm is used in association with other cryptographic-based algorithms to boost the performance of the encryption process which is deployed for the transition of classified and sensitive information into encrypted form and exchange of the same.

Examples of AES Algorithm Usage

  • Samsung and other manufacturers of storage devices, which are known as Solid Storage Devices (SSD), use the AES algorithm of 256-bit for saving the data.
  • The data we store on Google drive is an example of the usage of the AES algorithm. The cloud on which the user data is stored and visible on Google uses AES encryption method. It deploys a 256-bit encryption method, which is considered a more complex and highly secured method.
  • Facebook and WhatsApp messenger uses the AES encryption of 256-bit for securely transmitting and receiving the one-to-one message.
  • The Microsoft BitLocker process of encryption, which is by default present in the Windows system, also uses 128-bit and 256-bit AES encryption processes.
  • Internet of things (IoT) devices, self-encrypting software, and hard disk drives also use 128-bit and 256-bit AES encryption for the processing of data.

Features of AES Algorithm

  • AES encryption jumbles plain text information into a kind of cipher code that the unauthorized and third person can’t understand even if they crack it before the information reaches its desired destination. At the receiving end, the receiver has their secret code to unjumble the data back into the original, understandable text.
  • In this way, the AES encryption and decryption provisions protect crucial data from being intercepted by some unauthorized person or hacker and can be transmitted over the Internet through secure SSL channels. A fast-running example of exchanging such information is performing banking transactions through smartphones. It will be in encrypted form, and the information is visible to the user only.
  • The AES algorithm implementation is very cost-effective, and it is easy to use. In addition to this, there is no copyright issue associated with it. Thus, can be used globally by any person and organization.
  • The AES algorithm is easy to implement into software as well as hardware devices. It is very flexible.
  • VPN (Virtual Private Networks) deployed in switch for LAN and WAN networks also uses AES encryption by directing the IP address to a secure server located at the far end. This works efficiently for open source networks.

How the Advanced Encryption Standard (AES) Works

Each cipher encrypts and decrypts information in blocks of 128 bits utilizing cryptographic keys of 128, 192, and 256 bits, individually.

Figures utilize a similar key for encoding and decoding. The shipper and the recipient must both know and utilize a similar secret key.

The government authority classifies data into three classifications: Confidential, Secret, or Top Secret. All key lengths are can ensure Confidential and Secret levels. Highly classified data requires either 192-or 256-digit key lengths.

A round consists of a few handling steps that incorporate replacement, rendering, and blending of the info plaintext to change it into the last result of cipher text.

Advanced encryption design

Attacks on AES Encryption

There are various types of attacks that are possible in the AES encryption process. We have listed a few of them here.

#1) The most popular attack is side-a-channel attack. This involves gathering the information the device is using while performing cryptographic operations. It can use optical path information, audio leaks, text, or timing data to intercept the message sent.

These kinds of attacks can be minimized by carefully using the cipher code for encoding and decoding. One needs to keep scrambling the codes and keep randomly changing the codes be prevent information from being leaked.

#2) The second is brute-force attack. In this, the attacker keeps trying the various combinations of keys by using modern software to decode the cryptographic key used in the communication until he will reach the result. The 128-bit AES encryption is more mutable to these attacks. The remedy is to use the complex size cipher codes for encryption.

#3) The man-in-the-middle attack is the most common in the industry of computer security and cryptographic encryption.

In this type of attack, the attacker induces himself in the middle of two parties that are communicating with each other. It will pretend to be the victim user as the real party or host he is communicating with. He will intercept and gain all the database and control of the victim’s user. Now he will misuse it for his benefit.

#4) To get rid of these types of attacks, we should always use a secure way of communication. Use a strong authentication medium for communication with strong passwords. Always ignore the messages which come from untrusted sources.

Frequently Asked Questions

Q #1) Is AES secure?

Answer: Yes, the AES encryption method is secure, but to fully ensure this, we need to use strong passwords and need to deploy firewall and anti-malware programming in our system.

Q #2) Is AES symmetric or asymmetric?

Answer: The advanced encryption standard is symmetric. It uses a fixed 128, 192, or 256-bit key for both the encryption and decryption process.

Q #3) Can AES be cracked?

Answer: AES involves multiple steps of the encryption process in association with the deployment of complex mathematical expressions at each step. Thus, to crack the cipher coding is almost next to impossible.

Q #4) What is the difference between AES and DES?

Answer: DES is based on the Feistel network to encrypt the data. In this, the data block is breached into two portions before starting the encryption process. Meanwhile, the AES uses the permutation and substitution four-step method for encryption.

Q #5) What is AES Wi-Fi?

Answer: AES also supports the encryption method for all wireless networks. For Wi-Fi networks, AES generates the PSK or 802.1X keys to carry out the encryption. It further provides highly secure wireless networks by using IPsec security protocols.

Q #6) What is the difference between AES-128 and AES-256?

Answer: The difference lies in the number of rounds it performs to encrypt the data. The more the number of rounds, thus more secure the method of encryption. AES-256 performs 14 rounds while AES-128 performs 10 rounds of encryption. 128 and 256 is the length of the key used.

Q #7) What is the difference between AES vs RSA?

Answer: RSA uses asymmetric cipher for encryption and decryption of the information, whereas the AES algorithm uses symmetric cipher for encryption and decryption by using the secret key for coding and decoding of data information. It is the most secure method for encryption as very difficult to crack.

The RSA uses a public key with a combination of the private key for encryption and decryption.

Q #8) Does AES encryption have any security issues?

Answer: This method of encryption is very much secure, but it can be vulnerable to attack if the attacker will crack its cipher key. Thus, we need to secure and protect the encryption key from outsiders. For this, we should keep changing the passwords at regular intervals and need to use various layers of authentication to access the key.


AES encryption is the standard and most secure way of encryption of electronic data. In the above article, we have mentioned the steps we follow in the AES encryption and decryption process with the help of figures.

Also Read => Process to send an Encrypted Email

We have also explained what AES is with the help of examples and some of the frequently asked questions related to it.