Asymmetric key encryption (also known as public-key cryptography) uses a pair of keys: a public key for encryption and a private key for decryption (or vice versa for signing). Symmetric key encryption, on the other hand, uses the same key for both encryption and decryption. Let’s evaluate the options:
Option A ("AES"): AES (Advanced Encryption Standard) is a symmetric key encryption algorithm. It uses a single key (e.g., 128, 192, or 256 bits) for both encryption and decryption, making it a symmetric algorithm, not an asymmetric one.
Option B ("RSA"): RSA (Rivest-Shamir-Adleman) is an asymmetric key encryption algorithm. It uses a public key to encrypt data and a private key to decrypt it, making it a classic example of asymmetric cryptography.
Option C ("Diffie-Hellman"): Diffie-Hellman is an asymmetric key exchange algorithm. While it is primarily used for key exchange rather than direct encryption, it relies on asymmetric principles (public and private keys) to securely establish a shared secret, so it is considered part of asymmetric cryptography.
Option D ("DSA"): DSA (Digital Signature Algorithm) is an asymmetric algorithm used for digital signatures. It uses a pair of keys (public and private) for signing and verification, making it an asymmetric algorithm.
The correct answer is A, as AES is the only symmetric algorithm listed, aligning with the CAP syllabus under "Cryptography Fundamentals" and "Symmetric vs. Asymmetric Encryption."References: SecOps Group CAP Documents - "Cryptographic Algorithms," "Symmetric and Asymmetric Encryption," and "OWASP Cryptographic Storage Cheat Sheet" sections.
