350-701 Security Concepts Practice Question

Which cryptographic algorithm is a symmetric block cipher commonly used in modern VPNs and is considered secure?

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

AES

AES (Advanced Encryption Standard) is a widely used symmetric block cipher with key sizes of 128, 192, or 256 bits.

Answer analysis

For each option: why learners choose it and why it is or isn't the right answer here.

✓
AES
Why this is correct
AES is the standard symmetric cipher for secure communications.
✗
ECC
Why it's wrong here
ECC is an asymmetric algorithm based on elliptic curves.
✗
RSA
Why it's wrong here
RSA is an asymmetric algorithm used for encryption and digital signatures.
✗
3DES
Why it's wrong here
3DES is a symmetric cipher but is deprecated due to security concerns and slower performance.

Quick reference

Algorithm	Key Size	Block Size	Status	Notes
AES-128	128-bit	128-bit	Current standard	NIST approved; WPA3, TLS
AES-256	256-bit	128-bit	Current standard	Preferred for sensitive / govt data
3DES	112-bit effective	64-bit	Deprecated (2023)	Replaced by AES
DES	56-bit	64-bit	Broken	Cracked in < 24 h; never deploy
ChaCha20	256-bit	Stream cipher	Current	TLS 1.3, WireGuard

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