What is an example of a symmetric encryption algorithm?

AES, or Advanced Encryption Standard, is a widely used symmetric encryption algorithm characterized by its ability to use the same key for both encryption and decryption. In symmetric encryption, the confidentiality of data relies on both the sender and receiver having access to a shared secret key, which must be kept secure from unauthorized parties.

AES operates on fixed block sizes of 128 bits and allows for key sizes of 128, 192, or 256 bits. The design of AES incorporates multiple rounds of processing to enhance security. These rounds include a series of substitutions, permutations, and mixing of the plaintext to produce ciphertext, making it resistant to various attack vectors when implemented correctly.

In contrast, other options in the question represent asymmetric encryption or key exchange mechanisms. RSA and Elliptic Curve Cryptography are both asymmetric encryption algorithms, where different keys are used for encryption and decryption. Diffie-Hellman, meanwhile, is primarily a key exchange protocol that allows two parties to generate a shared secret over an insecure channel, rather than an encryption algorithm itself. Understanding these differences highlights why AES is classified as a symmetric encryption algorithm.