Difference Between AES and DES Ciphers

The main difference between AES and DES ciphers is the size of the key used for encryption. AES uses key sizes of 128, 192, or 256 bits, which offers robust security. In contrast, DES uses a relatively small 56-bit key size, which makes it vulnerable to brute-force attacks using modern computing power. 

The larger key size in AES makes it more difficult to crack than DES. And this is why AES has superseded and replaced DES as the standard encryption algorithm in most applications and industries.

Table of Content (TOC)

• Difference Between AES and DES
• What is AES Cipher?
• What is DES Cipher?
• AES and DES Cipher Example
• Key Differences Between AES and DES

Difference Between AES and DES

For better understanding and clarity, let's explore the difference between these two ciphers in a tabular format.

Benchmark	AES	DES
Cipher Type	Substitution-Permutation Network	Feistel Network
Block Size	128 bits	64 bits
Key Size	128, 192, or 256 bits	56 bits
Number of Rounds	10, 12, or 14 rounds (depending on key size)	16 rounds
S-Box (Substitution Box)	Highly nonlinear substitution boxes	Relatively simple substitution boxes
Security	Considered highly secure	Insecure due to small key size and cryptanalytic attacks
Cryptanalytic Resistance	Resistant to known attacks	Vulnerable to differential, linear, side-channel attacks, and brute-force attacks
Adoption and Usage	Widely adopted and used in various applications	Deprecated and replaced by AES and 3DES
Standardization	Adopted as a standard by NIST in 2001	Adopted as a standard in the 1970s, later withdrawn
Performance	Efficient and suitable for software and hardware implementations	Slower compared to modern ciphers

Must Read: What are Different Types of Cryptography?

What is AES Cipher?

AES (Advanced Encryption Standard) is a symmetric-key cipher, i.e., the same cryptographic key is used to encrypt and decrypt data. It is based on the Rijndael algorithm, which uses substitution-permutation networks to perform a series of substitutions (replacing input values with other values) and permutations (rearranging the order of the values) over multiple rounds to encrypt the data.

The AES cipher operates on a fixed block size of 128 bits (16 bytes) and supports key sizes of 128, 192, or 256 bits. The number of rounds in the cipher depends on the key size, with 10 rounds for 128-bit keys, 12 rounds for 192-bit keys, and 14 rounds for 256-bit keys.

The encryption process involves an initial AddRoundKey operation, followed by multiple rounds of the four main steps (SubBytes, ShiftRows, MixColumns, and AddRoundKey), and a final round without the MixColumns step. The decryption process follows a similar structure but is performed reversely.

AES is widely adopted and used in "n" number of applications, protocols, and systems due to its strong security, efficiency, and resistance to known cryptanalytic attacks when properly implemented.

Must Explore: Difference Between Cryptography and Steganography

What is DES Cipher?

DES (Data Encryption Standard) is a symmetric-key block cipher developed by IBM in the 1970s and later adopted as a standard by the U.S. government. It operates on 64-bit blocks of plaintext data using a 56-bit key (with an additional 8 bits used for parity checking). 

The DES cypher is based on the Feistel network structure that consists of multiple rounds (16 rounds in DES) of substitution and permutation operations. The encryption and decryption processes are similar, with the only difference being the order in which the round keys are applied. The decryption process uses the same steps as encryption but applies the round keys in reverse order.

While DES was considered secure when it was introduced, its 56-bit key size is now too small to withstand brute-force attacks from modern computing power, and various cryptanalytic attacks have been developed against it. Because of this, DES has been deprecated and replaced by more secure algorithms like AES and Triple DES (3DES).

Checkout courses on Encryption

AES and DES Cipher Example

Here's an example of encrypting the word "Hello" using both ciphers. This will help you better understand the difference between these two.

AES Encryption Example

• Plaintext: Hello
• Encryption Mode: CBC (Cipher Block Chaining), which requires an IV for the encryption process.
• Initialization Vector (IV): A randomly generated 128-bit value (to make it easy to understand, using a simple, non-random value): 0x000102030405060708090A0B0C0D0E0F
• Key Size: 128 bits (16 bytes)
• Key (in hexadecimal): 0x2b7e151628aed2a6abf7158809cf4f3c
• Process: The plaintext Hello is first padded according to PKCS#7 to fit a block size of 128 bits. The CBC mode encrypts each plaintext block by XORing it with the previous ciphertext block before encryption. The first block is XORed with the IV.

Note: The actual ciphertext generated would depend on the specific implementation details, the padding scheme and the IV used. 

DES Encryption Example

• Plaintext: Hello
• Encryption Mode: Electronic Codebook (ECB) (It does not require an IV and is generally not recommended for secure encryption due to its vulnerability to pattern analysis) 
• Key Size: 56 bits (within a 64-bit structure including parity bits)
• Key (in hexadecimal): 0x0e329232ea6d0d73
• Process: The plaintext Hello is padded to fit a block size of 64 bits. As ECB encrypts each block independently, the given key encrypts the padded plaintext block directly.

With a 56-bit key, there are approximately 7.2 x 10^16 possible keys for DES, a relatively small number for modern computing power. Meanwhile, with a 128-bit key, AES has approximately 3.4 x 10^38 possible keys, an astronomically larger number that makes a brute-force attack impractical with current technology.

Key Differences Between AES and DES

Here are the key differences between AES and DES ciphers:

• AES has a fixed block size of 128 bits, while DES operates on a block size of 64 bits. 
• DES uses the Feistel Network structure, while AES is based on the Substitution-Permutation Network.
• AES has a significantly larger key size than DES. AES supports key sizes of 128, 192, and 256 bits, while DES uses a 56-bit key size.
• AES is considered highly secure and resistant to known attacks. In contrast, DES has been deprecated due to its vulnerability to cryptanalytic attacks and small key size.