Advanced Encryption Standard

Difference between AES and DES ciphers

Advanced Encryption Standard (AES) is a highly trusted encryption algorithm used to secure data by converting it into an unreadable format without the proper key while Data Encryption Standard (DES) is a block cipher with a 56-bit key length that has played a significant role in data security. In this article, we are going to discuss the differences between AES and DES.

What is AES?

AES, short for Advanced Encryption Standard, is a widely utilized encryption method introduced in 2001. It was developed as a faster alternative to triple-DES, offering six times the speed. AES is one of the most commonly used symmetric block ciphers, operating on bytes instead of bits. This algorithm uses a symmetric key, meaning the same key is required for both encryption and decryption.

AES is renowned for its speed and robust security, making it ideal for safeguarding sensitive information in applications such as online banking, secure file storage, and wireless network security. Understanding AES and its role in cybersecurity ensures data protection against unauthorized access and cyberattacks.

Applications of AES

• Wireless Security: AES secures wireless networks, such as Wi-Fi, by maintaining data confidentiality and preventing unauthorized access.
• Data Storage and Transmission: It ensures secure data storage and transmission, protecting sensitive information.
• VPN (Virtual Private Network): AES secures VPN connections, enabling safe access to private networks over the internet.
• Disk Encryption: AES encrypts data on storage devices like hard drives and USB drives.
• Secure Messaging Apps: Many messaging platforms use AES to encrypt chats and file attachments.

What is DES?

Data Encryption Standard (DES) is an encryption algorithm created in 1977 to secure data by converting it into unreadable code. DES operates as a multi-round cipher, dividing the plaintext into two sections and processing them individually through steps like expansion, permutation, substitution, and XOR operations with round keys. Similar to AES, DES uses a symmetric key for both encryption and decryption.

Although DES was widely adopted for years, it is now considered less secure due to its short key length, making it susceptible to brute-force attacks. However, understanding DES is valuable since it laid the foundation for more secure algorithms like AES, shaping modern encryption practices.

Applications of DES

• Triple DES (3DES): A more secure version of DES, it applies the DES algorithm three times sequentially and is still used in older systems.
• Financial Transactions: DES was previously employed for securing financial transactions but has largely been replaced by AES.
• Legacy Systems: DES remains in use within some legacy systems for compatibility purposes.

Difference Between AES and DES

AES and DES are widely recognized encryption algorithms but differ significantly in terms of security, key length, and block size. While DES has become outdated due to its vulnerabilities, AES is the modern standard for encryption.

S.No	AES	DES
1.	Stands for Advanced Encryption Standard	Stands for Data Encryption Standard
2.	Introduced in 2001	Introduced in 1977
3.	Operates on bytes	Operates on bits
4.	Key lengths: 128, 192, or 256 bits	Key length: 56 bits
5.	Number of rounds depends on key length: 10 (128-bit), 12 (192-bit), 14 (256-bit)	Fixed 16 rounds of identical operations
6.	Based on a substitution-permutation network	Based on a Feistel network
7.	Open design rationale	Closed design rationale
8.	Selection process was open to public comment	Selection process was confidential
9.	AES is highly secure and a global standard	DES is vulnerable; 3DES offers improved security
10.	Rounds involve Byte Substitution, Shift Row, Mix Column, Key Addition	Rounds involve Expansion, XOR, Substitution, Permutation
11.	Encrypts 128 bits of plaintext	Encrypts 64 bits of plaintext
12.	Produces ciphertext of 128, 192, or 256 bits	Produces ciphertext of 64 bits
13.	Derived from an aside-channel square cipher	Derived from Lucifer cipher
14.	Designed by Vincent Rijmen and Joan Daemen	Designed by IBM
15.	No effective cryptanalysis attacks; minor side-channel vulnerabilities	Vulnerable to brute-force, linear cryptanalysis, and differential cryptanalysis
16.	Faster than DES	Slower compared to AES
17.	Highly flexible	Limited flexibility
18.	Efficient in both hardware and software	Best suited for hardware only

Advanced Encryption Standard (AES)

Advanced Encryption Standard (AES)

The Advanced Encryption Standard (AES) is a specification for encrypting electronic data, introduced by the U.S. National Institute of Standards and Technology (NIST) in 2001. Renowned for its robust security, AES is widely used today as a stronger alternative to DES and Triple DES, though it is more complex to implement. This article discusses AES, its working mechanism, encryption-decryption methods, and its applications.

What is Advanced Encryption Standard (AES)?

Advanced Encryption Standard (AES) is a reliable encryption algorithm designed to secure data by transforming it into an unreadable format without the correct key. Developed by NIST, AES supports key lengths of 128, 192, or 256 bits, offering high-level security against unauthorized access. It is an efficient solution for securing internet communications, protecting confidential data, and encrypting files. AES is a cornerstone of modern cryptography, globally acknowledged for its role in safeguarding information from cyber threats.

Key Points:

• AES is a block cipher.
• Supported key sizes: 128, 192, or 256 bits.
• Encrypts data in 128-bit blocks.
• AES processes 128-bit input blocks and produces 128-bit encrypted output using a substitution-permutation network, involving a sequence of operations that substitute and rearrange data.

How AES Cipher Works

AES operates on bytes of data rather than bits. Since the block size is 128 bits, the cipher processes 16 bytes (128 bits) of input data at a time.

The number of rounds in AES depends on the key size:

• 128-bit key: 10 rounds
• 192-bit key: 12 rounds
• 256-bit key: 14 rounds

Generation of Round Keys

The Key Schedule algorithm generates all round keys from the initial key. These round keys are used during the corresponding encryption rounds.

Encryption Process

AES represents each block as a 4×4 grid of 16 bytes in a column-major order:

[ b0  | b4  | b8  | b12 ]
[ b1  | b5  | b9  | b13 ]
[ b2  | b6  | b10 | b14 ]
[ b3  | b7  | b11 | b15 ]

Each round of AES involves the following steps:

• SubBytes
• ShiftRows
• MixColumns
• AddRoundKey

SubBytes: In this step, each byte is substituted using a lookup table called the S-box. Substitution ensures that a byte is not replaced with itself or its complement. This process produces another 4×4 grid.

ShiftRows: Each row is shifted left by a specific number of positions:

• The first row remains unchanged.
• The second row shifts left by one.
• The third row shifts left by two.
• The fourth row shifts left by three.

Before:                     After:
[b0 | b1 | b2 | b3]         [b0 | b1 | b2 | b3]
[b4 | b5 | b6 | b7]   →     [b5 | b6 | b7 | b4]
[b8 | b9 | b10 | b11]       [b10| b11| b8  | b9]
[b12| b13| b14 | b15]       [b15| b12| b13 | b14]

MixColumns: Each column undergoes a transformation using matrix multiplication with a predefined matrix:

[ c0 ]         [ 2  3  1  1 ]  [ b0 ]
[ c1 ]   =     [ 1  2  3  1 ]  [ b1 ]
[ c2 ]         [ 1  1  2  3 ]  [ b2 ]
[ c3 ]         [ 3  1  1  2 ]  [ b3 ]

AddRoundKey: The result from the previous step is XOR-ed with the corresponding round key. At this stage, the 16 bytes are treated as a 128-bit data block rather than a grid.

Decryption Process

Decryption reverses the encryption process. Each block undergoes 10, 12, or 14 rounds based on the key size.

The steps involved in decryption are:

• AddRoundKey
• Inverse MixColumns
• ShiftRows
• Inverse SubBytes

Inverse MixColumns: This step is similar to the Mix Columns step in encryption but differs in the matrix used to carry out the operation. Mix Columns Operation each column is mixed independent of the other. Matrix multiplication is used. The output of this step is the matrix multiplication of the old values and a constant matrix

[b0] = [ 10  13  9   11 ]   [ c0 ]
[b1] = [ 11  10  13  9  ]   [ c1 ]
[b2] = [ 9   11  10  13 ]   [ c2 ]
[b3] = [ 13  9   11  10 ]   [ c3 ]

Inverse SubBytes: Inverse S-box is used as a lookup table and using which the bytes are substituted during decryption. Function Substitute performs a byte substitution on each byte of the input word. For this purpose, it uses an S-box.

Applications of AES

AES is extensively used in securing data across various domains:

1. Wireless Security: Protects Wi-Fi networks, ensuring data confidentiality and preventing unauthorized access.
2. Database Encryption: Safeguards sensitive data in databases, including personal and financial information.
3. Secure Communications: Encrypts internet communications, emails, and voice/video calls to maintain confidentiality.
4. Data Storage: Encrypts data on hard drives, USB drives, and other storage media to prevent unauthorized access.
5. Virtual Private Networks (VPNs): Secures communication between devices and remote servers to protect transmitted data.
6. Password Storage: Encrypts passwords for secure storage, adding an extra layer of protection against breaches.
7. File and Disk Encryption: Secures sensitive data on computers, external devices, and cloud storage to safeguard information during transfer and storage.