AES128 vs AES256: A Detailed Comparison

AES-128 and AES-256 are both symmetric encryption algorithms, meaning they use the same key for both encryption and decryption. This makes them efficient for encrypting and decrypting data. The primary difference between them lies in the key length used. These AES standards were selected by the U.S. National Institute of Standards and Technology (NIST) as encryption standards after a rigorous evaluation process.

Due to the rapid development of cloud-based data applications, it has become essential to protect data during transmission. Various cryptography algorithms have been developed to ensure confidentiality, data protection, communication, authorization, and non-repudiation.

Cryptography techniques use mathematics to transform data into secret data that only authorized users can read. There are two main groups: symmetric and asymmetric cryptography. Symmetric cryptography uses the same key to encrypt and decrypt the message. Algorithms in this category include Blowfish, DES, 3DES, AES, CAS, RC6, TEA, IDEA, Serpent, Twofish, etc. Asymmetric cryptography uses two keys: one for encryption (the public key) and one for decryption (the private key). Algorithms in this category include DH, SSH, RSA, and SSL.

What is AES?

AES is a block cipher technique in which encryption is done group-wise at a time. It uses the same key in the encryption and decryption process, hence it is called symmetric cryptography.

There are two modes in which AES can be implemented: Counter mode and Output feedback mode. The operations performed by both algorithms are depicted in the figure above.

Benefits of AES Encryption

• Most robust security protocol due to its implementation in hardware and software.
• All the blocks follow a similar encryption procedure.
• It is stronger and faster compared to the Triple-DES algorithm.
• It uses encryption keys of longer size (128 bits or 192 bits or 256 bits), making it difficult to break.
• Official recognition by NIST increases their credibility and widespread use.

Drawbacks of AES Encryption

• The algorithm has a simple algebraic structure but is complex to implement in software.
• AES in counter mode is very challenging to implement in software with respect to performance and security.

128 bit encryption vs 256

AES-128 uses a 128-bit (16 bytes) key length for encryption. It is a block cipher, which means it processes data in fixed-size blocks (i.e., 128 bits at a time). Like AES-128 and AES-192, AES-256 is a symmetric encryption algorithm, meaning it uses the same key for both encryption and decryption.

While AES-256 offers increased security, it may be slower in terms of processing speed compared to AES-128 due to the longer key length. Both of these techniques follow the same process, except for the size of the keys. AES-128 uses a 128-bit key size, whereas AES-256 uses a 256-bit key size. There are 10 rounds in AES-128 and 14 rounds in the AES-256 encryption process.

The encryption process consists of different rounds as per key size, and each round follows the steps outlined below for both AES 128 and 256 encryption techniques:

• Subbytes
• Shiftrows
• MixColumns
• AddRoundKey

The decryption process for each round follows these four steps:

• Inverse ShiftRows
• Inverse substitute bytes
• AddRoundKey key
• Inverse mix columns

Here’s a simple example to illustrate the difference in key lengths between AES-128 and AES-256:

• AES-128 Key: [Vector of 1s and 0s with 128 length]
• AES-256 Key: [Vector of 1s and 0s with 256 length]

As you can see, the AES-256 key is longer and more complex than the AES-128 key.

Difference between AES 128 and AES 256

The following table compares AES 128 and 256 encryption techniques with respect to various parameters.

Conclusion

It’s important to note that the primary difference between AES128 and AES256 lies in the key length and, consequently, the potential security level they offer. AES-256 uses a longer key (256 bits) than AES-128 (128 bits), which theoretically makes it more resistant to brute-force attacks.

However, the choice between AES 128 vs 256 depends on the specific security requirements of an application, as well as performance considerations. Though the AES-256 key is longer and more complex than the AES-128 key, AES256 is not necessarily “better” than AES128 in all situations. AES 128 is still considered secure for most practical purposes and is often preferred for its computational efficiency, while AES 256 is used in scenarios where an extra layer of security is desired.