Network Defense Essentials (NDE) Practice Exam

What encryption algorithm uses the same key for both encryption and decryption and has a 128-bit block size?

1. RSA

2. AES

3. DES

4. Blowfish

The correct answer is: AES

The correct answer is the Advanced Encryption Standard (AES). AES is a symmetric encryption algorithm, meaning it utilizes the same key for both the encryption and decryption processes. This key management is a fundamental characteristic of symmetric encryption, distinguishing it from asymmetric encryption methods like RSA, which rely on a pair of keys for secure communication. AES specifically operates with a block size of 128 bits, which is one of its defining features. It processes data in fixed-size blocks, providing strong security and efficiency. AES supports key sizes of 128, 192, and 256 bits, enhancing its versatility and robustness against cryptographic attacks. The 128-bit block size makes it suitable for various applications requiring secure data transmission. In contrast, while DES (Data Encryption Standard) also uses the same key for encryption and decryption, it has a smaller block size of 64 bits, making it less secure compared to AES. Blowfish is another symmetric algorithm, but it typically uses a variable block size that can range from 32 bits to 448 bits, which does not align with the specified block size of 128 bits. RSA, on the other hand, is an asymmetric algorithm and does not fit the criteria of using the same key for both steps of the encryption