Which of the following best describes AES encryption?

AES (Advanced Encryption Standard) is indeed an iterative, symmetric-key block cipher that uses multiple key sizes, typically 128, 192, or 256 bits. This means that the same key is used for both encryption and decryption, which is characteristic of symmetric encryption. The "iterative" aspect refers to the way the encryption process is structured: it involves multiple rounds of processing where data is transformed through substitution and permutation operations.

Choosing from varying key sizes provides flexibility in terms of security levels; longer keys generally offer better security against brute-force attacks. AES operates on fixed-size blocks of data (128 bits) and goes through a series of well-defined transformations during each round of encryption, making it efficient and secure for many applications, such as securing data transmission over networks. In essence, AES offers both robustness and performance, which is why it is widely adopted as a standard for secure data encryption.