Symmetric key encryption algorithms use the same key for both encryption and decryption, while asymmetric algorithms use a pair of keys (public and private). Let's evaluate the options:
* Option A ("RC4"): RC4 is a symmetric key encryption algorithm. It is a stream cipher that uses a single key to both encrypt and decrypt data, though it is considered insecure due to known cryptographic weaknesses (e.g., biases in the keystream).
* Option B ("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, widely regarded as secure when properly implemented.
* Option C ("DES"): DES (Data Encryption Standard) is a symmetric key encryption algorithm. It uses a 56-bit key for both encryption and decryption, but it is now considered insecure due to its small key size and vulnerability to brute-force attacks.
* Option D ("RSA"): RSA (Rivest-Shamir-Adleman) is an asymmetric key encryption algorithm. It uses a public key to encrypt and a private key to decrypt, making it an asymmetric algorithm, not a symmetric one.
The correct answer is D, as RSA is the only asymmetric algorithm listed, aligning with the CAP syllabus under "Cryptography Fundamentals" and "Symmetric vs. Asymmetric Encryption."References: SecOps Group CAP Documents - "Symmetric Encryption Algorithms," "Asymmetric Encryption," and "OWASP Cryptographic Storage Cheat Sheet" sections.