Cisco Certified Network Associate (CCNA) Practice Exam

Which cryptographic algorithm is regarded as the most secure due to its flexibility in key sizes?

1. Data Encryption Standard (DES)

2. Triple DES (3DES)

3. Advanced Encryption Standard (AES)

4. Rivest Cipher (RC)

The correct answer is: Advanced Encryption Standard (AES)

The Advanced Encryption Standard (AES) is widely regarded as the most secure cryptographic algorithm primarily due to its flexibility in key sizes. AES supports key lengths of 128, 192, and 256 bits, allowing users to choose a key size that best suits their security requirements. This variety in key lengths contributes to AES's robust security profile; longer keys significantly increase the difficulty of a brute-force attack. Additionally, AES is based on the Rijndael algorithm, which was specifically designed to be secure against various forms of cryptographic attacks. Its design incorporates principles that ensure high performance on a wide range of hardware, making it suitable for both software and hardware implementations. In contrast, the other options have inherent limitations that affect their security. Data Encryption Standard (DES), for example, has been largely deprecated due to its short key length of 56 bits, which is no longer considered secure against modern computational power. Triple DES (3DES) improves upon this by applying DES three times, but it is still not as efficient or secure as AES, and it has been phased out in favor of AES. Rivest Cipher (RC) has various versions, but they also do not match the security assurances and widespread acceptance that AES has achieved. Overall,