easyMultiple Select

200-201 Practice Question: Which TWO of the following are symmetric…

Which TWO of the following are symmetric encryption algorithms? (Choose two.)

⚠ Common exam trap

Cisco often tests the distinction between symmetric encryption, asymmetric encryption, and key exchange protocols, so candidates mistakenly select Diffie-Hellman or ECC as encryption algorithms when they are actually used for key agreement or asymmetric operations.

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 (Option A) is correct because it is a symmetric block cipher that uses the same secret key for both encryption and decryption, operating on 128-bit blocks with key sizes of 128, 192, or 256 bits. 3DES (Option E) is also correct because it is a symmetric block cipher that applies the DES algorithm three times to each data block using the same shared secret key for encryption and decryption. RSA (Option B) is not correct because it is an asymmetric algorithm that uses a public key for encryption and a private key for decryption. Diffie-Hellman (Option C) is not correct because it is an asymmetric key-exchange protocol used to establish a shared secret, not a symmetric encryption algorithm itself. ECC (Option D) is not correct because it is an asymmetric public-key cryptography approach based on elliptic curve mathematics.

Answer analysis

Option-by-option breakdown

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 a symmetric block cipher: the same secret key both encrypts and decrypts data. It satisfies the question's requirement, unlike asymmetric algorithms such as RSA or Diffie-Hellman, which use separate public and private keys.
✗
RSA
Why it's wrong here
RSA is asymmetric, relying on a public/private key pair for encryption and key exchange, so it cannot serve as a symmetric algorithm. It is tempting because RSA is widely used for encrypting data and exchanging keys, but symmetric ciphers such as AES, 3DES or RC4 share one secret key between parties.
✗
Diffie-Hellman
Why it's wrong here
Diffie-Hellman is an asymmetric key-agreement protocol that lets two parties derive a shared secret over an untrusted channel; it performs no symmetric bulk encryption itself. It is tempting because the derived secret later feeds a symmetric cipher, but the algorithm named here is not the symmetric algorithm being asked for.
✗
ECC
Why it's wrong here
ECC is asymmetric public-key cryptography based on elliptic-curve mathematics, used for key exchange and digital signatures rather than symmetric bulk encryption. It is tempting because ECC is efficient and often paired with symmetric ciphers, but symmetric algorithms such as AES, DES and 3DES use a single shared secret key.
✓
3DES
Why this is correct
3DES is symmetric: it applies the DES cipher three times using shared secret keys for encryption and decryption. It meets the question's criterion, unlike asymmetric algorithms such as RSA or elliptic-curve cryptography, which rely on mathematically related key pairs.

Quick reference

Symmetric Encryption Algorithm Comparison

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

Go deeper

200-201 Practice Question: Which TWO of the following are symmetric…

Why each option matters

Option-by-option breakdown

Symmetric Encryption Algorithm Comparison

Related to this question