# CISSP Domain 3 questions – Asymmetric Encryption quiz

Question 1: Which of the following is a true difference between an asymmetric and symmetric algorithm?
Symmetric algorithms are faster because they use substitution and transposition
This is Correct. This is because symmetric algorithms carry out relative simplistic mathematical functions on the bits during the encryption and decryption processes. They substitute and scramble (transposition) bits, which is not overly difficult or intensive. The reason that it is hard to break this type of encryption is because they carry out this type of functionality over and over again. Asymmetric algorithms use much more complex mathematics to carry out their functions, which require more processing time, which is why they are slower than symmetric algorithms.
Asymmetric algorithms are slower because they use substitution and transposition
This is Incorrect.
Asymmetric algorithms are best implemented in hardware and symmetric in software
This is Incorrect.
Asymmetric algorithms are more vulnerable to frequency analysis attacks
This is Incorrect.
Question 2: Which one of the following encryption algorithms is now considered insecure?
Merkle-Hellman Knapsack
This is Correct. The Merkle-Hellman Knapsack algorithm, which relies on the difficulty of factoring super-increasing sets, has been broken by cryptanalysts.
Elliptic Curve Cryptography
This is Incorrect.
RSA
This is Incorrect.
El Gamal
This is Incorrect.
Question 3: Acme Widgets currently uses a 1,024-bit RSA encryption standard companywide. The company plans to convert from RSA to an elliptic curve cryptosystem. If it wants to maintain the same cryptographic strength, what ECC key length should it use?
160 bits
This is Correct. The elliptic curve cryptosystem requires significantly shorter keys to achieve encryption that would be the same strength as encryption achieved with the RSA encryption algorithm. A 1,024-bit RSA key is cryptographically equivalent to a 160-bit elliptic curve cryptosystem key.
512 bits
This is Incorrect.
1024 bits
This is Incorrect.
20148 bits
This is Incorrect.
Question 4: If a 2,048-bit plaintext message were encrypted with the El Gamal public key cryptosystem, how long would the resulting ciphertext message be?
4096 bits
This is Correct. The major disadvantage of the El Gamal cryptosystem is that it doubles the length of any message it encrypts. Therefore, a 2,048-bit plain-text message would yield a 4,096-bit ciphertext message when El Gamal is used for the encryption process.
8192 bits
This is Incorrect.
2048 bits
This is Incorrect.
1024 bits
This is Incorrect.
Question 5: Which cryptographic algorithm forms the basis of the El Gamal cryptosystem?
Diffie-Hellman
This is Correct. The El Gamal cryptosystem extends the functionality of the Diffie-Hellman key exchange protocol to support the encryption and decryption of messages.
RSA
This is Incorrect.
3DES
This is Incorrect.
IDEA
This is Incorrect.
Question 6: If we want to implement a type of encryption that uses discrete logarithms, which of these could we choose?
ECC
This is Correct. Computer scientists and mathematicians believe that it is extremely hard to find x, even if P and Q are already known. This difficult problem, known as the elliptic curve discrete logarithm problem, forms the basis of elliptic curve cryptography. It is widely believed that this problem is harder to solve than both the prime factorization problem that the RSA cryptosystem is based on and the standard discrete logarithm problem utilized by Diffie–Hellman and El Gamal. Refer to our post on Hash Functions
Twofish
This is Incorrect.
AES
This is Incorrect.
DES
This is Incorrect.
Question 7: We have 100 users all needing to communicate with each other. If we are using asymmetric encryption how many keys would we need?
200
This is Correct. Asymmetric encryption uses 2 keys per user, so we would need 200 keys.
300
This is Incorrect.
4950
This is Incorrect.
2000
This is Incorrect.
Question 8: Jack is looking at different types of encryption. Which of these is a type of asymmetric encryption?
RSA
This is Correct. RSA is asymmetric. 3DES, RC6 and Twofish are all symmetric forms of encryption.
DES
This is Incorrect.
3DES
This is Incorrect.
Twofish
This is Incorrect.
Question 9: What is your public key in asymmetric encryption?
Shared
This is Correct. Asymmetric Encryption uses 2 keys: a Public Key and a Private Key (Key Pair). Your Public Key is publicly available. Used by others to encrypt messages sent to you. Since the key is asymmetric, the ciphertext can’t be decrypted with your public Key. Your Private Key – You keep this safe. You use it to decrypt messages sent with your public key.
Secret
This is Incorrect.
Used by you to decrypt messages sent to you.
This is Incorrect.
used by someone else to decrypt messages from you.
This is Incorrect.
Question 10: A senior VP stops you in the cafeteria because you are one of those IT people. She asks you questions about Public Key Infrastructure (PKI). After you explain it at a high level, they ask for more detail. You could tell them PKI uses which of these?
All of these.
This is Correct. PKI (Public Key Infrastructure): Uses Asymmetric and Symmetric Encryption as well as Hashing to provide and manage digital certificates. To ensure PKI works well, we keep the private key secret.
Symmetric Key Algorithm
This is Incorrect.
Asymmetric Key Algorithm
This is Incorrect.
Hashing
This is Incorrect.
Question 11: When we have our private and public keys in key escrow, what does that mean?
Someone keeping a copy of our keys, often law enforcement.
This is Correct.
The server we keep our public and private keys on.
This is Incorrect.
The private key have on my system.
This is Incorrect.
The public key available to everyone.
This is Incorrect.

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