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What is AES?

These days, security is the primary concern for everyone in IT. Given that $155 billion in expenditure on information security and risk management is expected to increase to $172 billion in 2022, according to Gartner, it must be. While there are many tools you can purchase to protect your data, encryption is one security tool that every computer user should be familiar with. A cryptographic "break" for cryptographers is anything quicker than a brute-force assault, which involves decrypting one trial key at a time. Thus, a break can produce outcomes that are now technologically impossible. Although theoretical breakdowns are useless, they occasionally reveal vulnerability patterns. In 2006, conducted the greatest known successful brute-force assault on a widely used block-cipher encryption technique using a 64-bit RC5 key.

Why Encryption Is Useful?

Encryption is a technique for making data messages or files unreadable, guaranteeing that only a person with the proper authorization may access that data. Data is encrypted using sophisticated algorithms, and the same data is then decrypted using a key that is supplied by the message's sender. Information is kept secret and confidential by encryption while it is being stored or sent. Any unauthorized access will just reveal a disorganized collection of bytes.

You should be familiar with the following concepts related to encryption:


Algorithms, sometimes referred to as ciphers, are the guidelines or directions for the encryption procedure. The efficiency of the encryption depends on the key length, capabilities, and characteristics of the employed encryption method.


Decryption is the process of turning unintelligible cipher text into understandable data.


A random string of bits called an encryption key is used to encrypt and decode data. Longer keys are more difficult to break, and each key is different. Public keys typically have a length of 2048 bits, whereas private keys often have 128 or 256 bits.

Asymmetric and symmetric cryptographic key schemes are both available.

Symmetric Keys Systems

Everyone who accesses the data in a symmetric key system uses the same key. To maintain anonymity, encryption and decryption keys must also be kept a secret. While this is technically conceivable, it is impracticable to employ symmetric encryption for extensive commercial usage due to the need for securely distributing the keys to guarantee the right controls are in place.

Asymmetric Keys Systems

A public/private key system, sometimes referred to as an asymmetric key system, employs two keys. The private key is the only key that is kept a secret, although everyone else has access to the other key. The public key is what is known as. Due to the mathematical connection between the private and public keys, only the appropriate private key may decode data that has been encrypted with the help of the public key.

Practice of Encryption

Here's an illustration of how encryption functions using the email-friendly programme Pretty Good Privacy (PGP), often known as GnuPG or GPG for fans of open-source software. Let's say I want to message you privately. I use one of the programmes on the following list to encrypt it.

The advice is as follows:

The message is transformed into a garbled tangle of random characters after encryption. But if you have the key I provide you, you may unlock it and discover the message's original content.

Even if someone manages to access your network or system, encryption works to keep prying eyes out of your company, whether it's in transit like our hot dog party email or sitting on your hard drive.

The technology comes in a range of shapes and sizes, with key size and strength often indicating the biggest variations from one type to the next.

Advanced Encryption Standard (AES)

Two Belgian cryptographers, Joan Daemen and Vincent Rijmen, created the AES variation of the Rijndael block cypher and presented a proposal to NIST as part of the AES selection process. A family of cyphers called Rijndael has various key and block sizes. NIST chose three Rijndael family members for AES, each having a 128-bit block size but three distinct key lengths: 128, 192, and 256 bits.

The symmetric encryption algorithm with the most widespread application is called AES, or Advanced Encryption Standard. It is mostly utilized to encrypt and safeguard electronic data. Because it is quicker and more effective than DES (Data encryption standard), it was used to replace DES. Three block ciphers make up the AES encryption system, which is used to encrypt data. NIST (National Institute of Standards and Technology) created AES in 1997. It was created to take the place of DES, which was sluggish and open to many assaults. In order to fix DES's flaws, a new encryption algorithm was developed. AES was subsequently released on November 26, 2001.

The United States National Institute of Standards and Technology (NIST) developed the Advanced Encryption Standard (AES) as a standard for the encryption of electronic data in 2001. Despite being more difficult to build, AES is still commonly used because it is substantially stronger than DES and triple DES.

Things to keep in mind

  • A block cipher is AES.
  • Key sizes range from 128 to 256 bits.
  • Data is encrypted in chunks of 128 bits.

As a result, it generates 128 bits of encrypted cipher text as output from 128 bits of input. AES operates utilizing a chain of linked operations that replace and shuffle the input data, which is known as the substitution-permutation network concept. For every extra bit of key length, the key space grows by a factor of 2, which results in a doubling of the average brute-force key search time assuming every conceivable value of the key is equiprobable. This suggests that as key length rises, the difficulty of a brute-force search grows exponentially. Given that there are cyphers with extremely lengthy keys that have been discovered to be weak, key length alone does not guarantee security against assaults.

The algebraic foundation of AES is pretty straightforward. Nicolas Courtois and Josef Pieprzyk published a theoretical assault in 2002 called the "XSL attack" that claimed to demonstrate a flaw in the AES algorithm, largely as a result of the nonlinear components' lack of complexity.

Workings of the cipher

AES operates on data in bytes as opposed to bits. The cipher analyses 128 bits (or 16 bytes) of the incoming data at a time since each block is 128 bits in size.

According to the key length, the number of rounds will vary as follows:

  • 10 rounds using a 128-bit key
  • 12 cycles for a 192-bit key
  • 14 cycles for a 256-bit key

Developing round keys:

All the round keys from the key are calculated using a Key Schedule method. Therefore, several separate round keys that will be used in the corresponding round of the encryption are created using the original key.


AES considers each block as a 16 byte (4 byte x 4 byte = 128) grid in a column major arrangement.

[ b0 | b4 | b8 | b12 |

| b1 | b5 | b9 | b13 |

| b2 | b6 | b10| b14 |

| b3 | b7 | b11| b15 ]

What is AES

Each round comprises of 4 steps:

  • SubBytes
  • ShiftRows
  • MixColumns
  • Add Round Key

The MixColumns round is absent from the final round. In the algorithm, SubBytes handle substitution, while ShiftRows and MixColumns handle permutation.


This action carries out the substitution.

Each byte is replaced with another byte in this phase. The S-box, another name for the lookup table used, is employed. A byte is never replaced by itself or by a byte that is a complement of the current byte because of the manner this substitution is carried out. This process yields the same 16-byte (4 x 4) matrix as previously.

The permutation is applied in the next two phases.

ShiftRows :

This step is just as it sounds. Each row is shifted a particular number of times.

  • The first row is not shifted
  • The second row is shifted once to the left.
  • The third row is shifted twice to the left.
  • The fourth row is shifted thrice to the left.

(A left circular shift is performed.)


This step is basically a matrix multiplication. Each column is multiplied with a specific matrix and thus the position of each byte in the column is changed as a result.

This step is skipped in the last round.

Round Keys added:

The output of the preceding step is now XORed with the relevant round key to get the result. In this case, the 16 bytes are simply regarded as 128 bits of data and not as a grid.

128 bits of encrypted data are returned as output after each cycle. This procedure is continued until all of the data that needs to be encrypted has gone through it.


The steps in the rounds are easily reversible since they each have an opposite that, when used, undoes the modifications. Depending on the key size, each of the 128 blocks is processed via 10, 12, or 14 rounds.

Following are the phases of each round of decryption:

  • Add round key
  • Inverse MixColumns
  • ShiftRows
  • Inverse SubByte

The decryption process is the encryption process done in reverse so i will explain the steps with notable differences.

Inverse MixColumns:

This step is similar to the MixColumns step in encryption, but differs in the matrix used to carry out the operation.

Inverse SubBytes: Inverse S-box is used as a lookup table and using which the bytes are substituted during decryption.


  • Many applications that call for secure data storage and transfer frequently employ AES.
  • AES is used in wireless network security, such as that of Wi-Fi networks, to guarantee data secrecy and thwart unauthorized access.
  • AES may be used to encrypt private information kept in databases. This aids in preventing unauthorized access to private data such as financial records, personal information, and other data in the event of a data breach.
  • AES is frequently used in protocols for voice/video conversations, email, instant messaging, and internet communications. It makes sure the information is kept private.
  • Data storage: To prevent unauthorized access in the event of loss or theft, sensitive data is encrypted using AES and stored on hard discs, USB drives, and other storage devices.
  • AES is frequently used in Virtual Private Networks (VPN) protocols to protect communication between a user's device and a remote server. It makes sure that data transmitted and received via the VPN is secure and cannot be read by eyes droppers.
  • Password Security: AES encryption is frequently used to store passwords securely. Passwords are saved in encrypted form rather than plaintext. In the event of unauthorized access to the storage, this adds an additional layer of protection and safeguards user credentials.
  • File and Disc Encryption: On PCs, external storage devices, and cloud storage, AES is used to encrypt files and folders. It safeguards sensitive data during data transport or storage to stop unauthorized access.


AES uses keys of lengths of 128, 192, and 256 bits.

  • It is adaptable and has software and hardware implementations.
  • It offers excellent security and can stop many threats.
  • Since it is copyright-free, anybody can use it anywhere in the world.
  • For 128 bit keys, there are 10 rounds of processing.


  • It may be used with both software and hardware.
  • It offers consumers a high level of security.
  • It offers one of the top encryption open source solutions.
  • This algorithm is quite reliable.


  • For encryption, multiple rounds are necessary.
  • Software implementation is challenging.
  • It requires extensive processing at several stages.
  • Implementation is challenging when performance is a factor.


Now that AES is built into the CPU, programs that use it for encryption and decryption may operate more quickly and securely (with throughput of several GB/s). Even though the AES algorithm has been around for 20 years, we haven't succeeded in breaking it because, even with today's technology, it is impossible. As of yet, the algorithm's implementation is the only area of risk.

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