AES Modes of Operation for Authentication

AC.

The Advanced Encryption Standard (AES) is a widely used symmetric encryption algorithm that provides confidentiality to data by encrypting it with a secret key. However, AES alone does not provide authentication, which means that an attacker could potentially modify the encrypted data without the recipient's knowledge.

To address this issue, AES can be used in conjunction with an authentication mode of operation that ensures the integrity and authenticity of the encrypted data. Two AES modes of operation that provide authentication are:

1. CCM (Counter with CBC-MAC): CCM is a mode of operation that combines counter mode (CTR) encryption with cipher-block chaining message authentication code (CBC-MAC) authentication. CCM provides both confidentiality and authentication and is commonly used in wireless networks, Bluetooth, and Zigbee.

2. GCM (Galois/Counter Mode): GCM is a mode of operation that combines CTR encryption with Galois message authentication code (GMAC) authentication. GCM provides both confidentiality and authentication and is commonly used in network protocols such as IPsec and TLS.

On the other hand, the remaining answer choices are:

• CBC (Cipher Block Chaining): CBC is a mode of operation that provides confidentiality but does not provide authentication. CBC is vulnerable to padding oracle attacks and is not recommended for new designs.
• DSA (Digital Signature Algorithm): DSA is not a mode of operation for AES encryption. It is a digital signature algorithm used for verifying the authenticity of digital documents and messages.
• CFB (Cipher Feedback): CFB is a mode of operation that provides confidentiality but does not provide authentication. CFB is less commonly used than other modes of operation.

Therefore, the correct answers are A. CCM and C. GCM as they provide authentication in addition to confidentiality.