Which of the following are key sizes used by AES?

The key sizes used by AES (Advanced Encryption Standard) are 128, 192, and 256 bits. This flexibility in key size is essential for providing varying levels of security appropriate to the sensitivity of the data being protected.

AES is designed to ensure strong security while also allowing for efficient processing, which is achieved through these specific key sizes. The 128-bit key offers a balance between security and performance, 192 bits enhances security further, and 256 bits provides the highest level of security for extremely sensitive data.

The other options listed do not accurately represent the key sizes defined by AES; for instance, AES does not support a 64-bit key, nor does it use a 512-bit key, as those sizes are not part of the AES specification. This careful selection of key sizes ensures that AES remains efficient while providing robust security features suitable for a wide range of applications in data encryption.