Quiz 08. Cryptography - Part II. Symmetric & Asymmetric Cryptography (Final)

Kevin is using Diffie-Hellman to share confidential information with Tina. The following phrases explain what he must do. Select the most appropriate phrases to describe the process. Kevin combines his own 1._____ with the 2._____ to produce a 3._____. 1. Kevin combines his own 2. with the 3. to produce a

1. Kevin combines his own a) private key 2. with the b) public key belonging to Tina 3. to produce a c) unique secret key shared by Kevin and Tina

An Advanced Encryption Standard (AES) key may not be: a) 16 bits in length. b) 128 bits in length. c) 256 bits in length. d) 192 bits in length.

a) 16 bits in length.

We are trying to decide between a public-key and a secret-key cryptographic solution. Which of the following criteria would encourage us to choose the public-key solution? Select all that apply best to public-key cryptography. a) Attackers should not be able to penetrate the whole system simply by attacking a central crypto server. b) We are providing the service to an established user community whose members are already identified. c) The process of adding new users must be easy to delegate. d) The system can apply a lot of computational power to cryptographic operations. e) When someone loses the privilege to access the system, we must be able to revoke that user's access rights immediately. f) The system will always be limited to a small user community.

a) Attackers should not be able to penetrate the whole system simply by attacking a central crypto server. c) The process of adding new users must be easy to delegate. d) The system can apply a lot of computational power to cryptographic operations.

The principal weakness of ____________________ is its short key size. a) DES b) Triple DES (3DES) c) AES (Rijndael) d) Serpent

a) DES

True or False? After changing an encryption key, all backup copies of the protected file are also protected by the new key. a) False b) True

a) False

True or False? Holding all other factors constant, 3DES (Triple-DES) can encrypt a message faster than AES. a) False b) True

a) False

True or False? The Diffie-Hellman cipher is a full encryption method. a) False b) True

a) False

True or False? There is a single, global public-key infrastructure (PKI). a) False b) True

a) False

Kevin is using RSA to send information to Tina. The following phrases explain what he must do. Select the most appropriate phrases to describe the first part of the process. Kevin encrypts a 1._____with the 2._____ to produce a(n) 3._____. a) Kevin encrypts a b) with the c) to produce a(n)

a) Kevin encrypts a a. randomly-generated secret key b) with the a. public key belonging to Tina c) to produce a(n) a. encrypted key (a.k.a. wrapped key)

The phrases below describe terms and entities associated with encryption. Match the term or entity with its description. a) No single person is universally trusted to sign certificates; individual users decide who they trust to sign certificates b) Used to validate public keys and to use them safely c) A trusted third party that issues certificates

a) No single person is universally trusted to sign certificates; individual users decide who they trust to sign certificates a. Web of trust b) Used to validate public keys and to use them safely a. Public-key infrastructure (PKI) c) A trusted third party that issues certificates a. Certificate authority

Provide the best matches below between terms and concepts. a) Number of keys in a public-key algorithm b) Number of keys in a secret-key algorithm c) Key secrecy in a secret-key algorithm d) Symmetry of keys in a public-key algorithm

a) Number of keys in a public-key algorithm a. Two different, but related keys b) Number of keys in a secret-key algorithm a. One key c) Key secrecy in a secret-key algorithm a. All keys are kept secret d) Symmetry of keys in a public-key algorithm a. Uses asymmetric keys

What role does the trusted third party (CA) serve in public-key certificates? Select all that apply. a) Publishes its own public key so others can use it to verify the certificates it issues b) Signs public-key certificates using its public key c) Publishes its own private key so others can use it to verify the certificates it issues d) Signs public-key certificates using its private key

a) Publishes its own public key so others can use it to verify the certificates it issues d) Signs public-key certificates using its private key

True or False? A certificate authority is a trusted third party that issues certificates on behalf of some organization. a) True b) False

a) True

True or False? Changing a single bit of a block cipher's input affects the entire output block. a) True b) False

a) True

True or False? SHA1 is considered more secure than MD5. a) True b) False

a) True

True or False? The size of an SHA256 hash digest is 256 bits. a) True b) False

a) True

True or False? When you visit a website with an "https" prefix in the address, the site uses encryption on the web data it sends and receives. a) True b) False

a) True

Bob and Kevin are both using symmetric crypto to exchange sensitive information with other people. Although Bob and Kevin sometimes exchange sensitive information using a symmetric crypto and a shared secret, Bob doesn't want Kevin eavesdropping on his messages to others, and vice versa. They need to choose a widely available (i.e., in public domain) symmetric crypto algorithms and a key for each of their communication partners. Which of the following choices will protect one from eavesdropping by the other? Select all that apply. a) Use different algorithms and different keys. b) Use the same algorithm and different keys. c) Use the same algorithm and the same key. d) Use different algorithms and the same key.

a) Use different algorithms and different keys. b) Use the same algorithm and different keys.

Which of the following is a block cipher algorithm? a) Serpent b) All of the others c) AES d) DES e) RC6

b) All of the others

Which of the following can help to avoid problems with reused encryption keys? a) Change the CPU b) Combine the key with a nonce/salt c) Use the same passphrase d) Clear your computer's RAM

b) Combine the key with a nonce/salt

True or False? A digital signature uses symmetric keys to sign or verify digital data. a) True b) False

b) False

True or False? AES was introduced before DES. a) True b) False

b) False

What is the single most important feature of stream cipher encryption that could prevent reused key streams? a) Using a truly random crypto key b) Incorporating a nonce (salt) c) Using a large crypto key d) Incorporating a one-way hash

b) Incorporating a nonce (salt)

Which of the following is not a symmetric cryptography algorithm? a) Serpent b) SHA-2 c) IDEA d) Blowfish

b) SHA-2

Alice transmits a message to Bob using a stream cipher. During transmission, an error causes a single bit in the ciphertext to change. How does this affect the decrypted message? a) The decryption process corrects the error. b) The decrypted message contains a 1-bit error in the same location. c) The message is readable up to the bit containing the error and scrambled after that point. d) The entire message is unreadable after it is decrypted.

b) The decrypted message contains a 1-bit error in the same location.

True or False? A keyed hash gives us a way to verify that some of our own data has not been modified by an attacker or someone who doesn't have the secret key. a) False b) True

b) True

True or False? You can wrap a secret key with RSA. a) False b) True

b) True

Encrypting an encryption key using another encryption algorithm with a different key is called: a) key exchange. b) key wrapping. c) symmetric cryptography. d) modular inversing.

b) key wrapping.

Which of the following is not a symmetric cryptography algorithm? a) RC4 b) AES c) RSA d) RC6

c) RSA

In __________________, an encryption operation is performed up to three times, each of which may use a different 56-bit key. a) RC6 b) DES c) Triple DES (3DES) d) AES (Rijndael)

c) Triple DES (3DES)

_____________________ algorithm performs 10, 12, or 14 rounds of encryption operations with a 128, 192, or 256-bit key respectively a) Triple DES (3DES) b) RC6 c) DES d) AES (a.k.a. Rijndael)

d) AES (a.k.a. Rijndael)

Bob and Alice want to exchange a shared secret key using RSA. Which of the following components must Bob use to share the secret with Alice? a) Bob's private key alone b) Alice's public key and Bob's private key c) Alice's private key and Bob's public key d) Alice's public key alone

d) Alice's public key alone

Which of the following is a stream cipher algorithm? a) RC5 (Rivest's cipher 5) b) RC6 (Rivest's cipher 6) c) RC2 (Rivest's cipher 2) d) RC4 (Rivest's cipher 4)

d) RC4 (Rivest's cipher 4)