Chapter 7 Questions
_______ offers a mechanism to accomplish four security goals: confidentiality, integrity, authentication, and nonrepudiation. a) Security association (SA) b) Transport Layer Security (TLS) c) Cryptography d) None of these is correct.
C) Cryptography
T/F: A strong hash function is designed so that it is nearly impossible for a forged message to result in the same hash as a legitimate message.
True
T/F: Encryption ciphers fall into two general categories: symmetric (private) key and asymmetric key (public)
True
T/F: The two basic types of ciphers are transposition and substitution.
True
Alice would like to send a message to Bob using a digital signature. What cryptographic key does Alice use to create the digital signature? a) Alice's private key b) Bob's public key c) Alice's public key d) Bob's private key
a) Alice's private key The sender of a message uses his or her own private key to encrypt a hash of the message. This encrypted value is the digital signature.
When Alice receives a message from Bob, she wants to be able to demonstrate to Miriam that the message actually came from Bob. What goal of cryptography is Alice attempting to achieve? a) Nonrepudiation b) Authentication c) Integrity d) Confidentiality
a) Nonrepudiation Nonrepudiation enables you to prevent a party from denying a previous statement or action. Using asymmetric key cryptography, you can prove mathematically—usually to the satisfaction of a judge or jury—that a particular party did indeed originate a specific message at a specific time.
Which set of characteristics describes the Caesar cipher accurately? a) Symmetric, stream, substitution b) Asymmetric, block, substitution c) Symmetric, block, transposition d) Asymmetric, stream, transposition
a) Symmetric, stream, substitution The Caesar cipher is an example of a substitution cipher because it changes the letters in a message. It is not a transposition cipher because it does not rearrange the letters. It is also a stream cipher rather than a block cipher because it works on one character at a time. It is a symmetric, not an asymmetric, cipher because both the sender and receiver use the same key.
A _______ signature is a representation of a physical signature stored in a digital format. a) digital b) digitized c) private key d) public key
a) digital
A __________ is used to detect malicious changes to data. a) hash function b) checksum c) hash value d) KDC
a) hash function
_______ corroborates the identity of an entity, whether the sender, the sender's computer, some information a) nonrepudiation b) confidentiality c) integrity d) authentication
a) nonrepudiation
An encryption cipher that uses the same key to encrypt and decrypt is called a(n) ________ key. a) symmetric (private) b) asymmetric (public) c) encrypting d) hash e) None of these
a) symmetric (private)
Bob received a message from Alice that contains a digital signature. What cryptographic key does Bob use to verify the digital signature? a) Bob's private key b) Alice's public key c) Alice's private key d) Bob's public key
b) Alice's public key The recipient of a digitally signed message uses the sender's public key to verify that the digital signature is authentic.
Alice would like to send a message to Bob securely and wishes to use asymmetric encryption to encrypt the contents of the message. What key does she use to encrypt this message? a) Alice's public key b) Bob's public key c) Bob's private key d) Alice's private key
b) Bob's public key If you were encrypting a message to protect its confidentiality and integrity, you would use the recipient's public key
Bob is sending a message to Alice. He wants to ensure that nobody tampers with the message while it is in transit. What goal of cryptography is Bob attempting to achieve? a) Nonrepudiation b) Integrity c) Authentication d) Confidentiality
b) Integrity Integrity ensures that no one, not even the sender, changes information after transmitting it. If a message does not decrypt properly, someone or something probably changed the ciphertext in transit.
Which approach to cryptography uses highly parallel algorithms that could solve problems in a fraction of the time needed by conventional computers? a) Asymmetric cryptography b) Quantum cryptography c) Classic cryptography d) Elliptic curve cryptography
b) Quantum cryptography
The act of scrambling plaintext into ciphertext is known as: a) decryption b) encryption c) plaintext d) cleartext
b) encryption
Which cryptographic attack is relevant in only asymmetric key systems and hash functions? a) Known plaintext b) Ciphertext only c) Chosen ciphertext d) Chosen plaintext
c) Chosen ciphertext In a chosen-ciphertext attack, cryptanalysts submit data, which is coded with the same cipher and key as they are trying to break, to the decryption device to see either the plaintext output or the effect the decrypted message has on a system.
Which of the following is not an objective of cryptanalysis, the process of breaking codes? a) Derive the algorithm used by a particular cipher b) Determine the key used to encrypt a target message c) Encrypt the plaintext of a target message d) Solve the general mathematical problem underlying the cryptography
c) Encrypt the plaintext of a target message An objective of cryptanalysis is to derive the plaintext of a target message, not encrypt it.
Some ciphers, regardless of type, rely on the difficulty of solving certain mathematical problems, which is the basis for asymmetric key cryptography. Which of the following is a branch of mathematics that involves multiplicative inverses that these ciphers use? a) Factoring small numbers b) Quantum physics c) Field theory d) Subset sum problems
c) Field theory These ciphers use a branch of mathematics known as field theory. A field is any domain of numbers in which every element other than 0 has a multiplicative inverse. For example, all rational numbers form a field; therefore, given x ≠ 0, you can always compute 1/x. Fields do not have to be infinite. Instead of counting to infinity, you can restart counting after reaching a particular value
Which information security objective verifies the action to create an object or verifies an object's existence by an entity other than the creator? a) Validation b) Certification c) Witnessing d) Authorization
c) Witnessing Witnessing is verifying the action used to create an object or verify an object's existence. Certification is a similar concept but allows for the endorsement of information by a trusted party.
Maria receives a ciphertext message from her colleague Wen. What type of function does Maria need to use to read the plaintext message? a) Encryption b) Hashing c) Validation d) Decryption
d) Decryption Decryption is the process of unscrambling ciphertext into plaintext. Encryption is the process of scrambling plaintext into ciphertext.
Security objectives add value to relationships between businesses or between businesses and their customers. Which objective binds a message or data to a specific entity? a) Receipt and confirmation b) Message authentication c) Nonrepudiation d) Digital signature
d) Digital signature A digital signature binds a message or data to a specific entity. This is not a digitized signature, which is an image of an electronically reproduced signature.
An algorithm used for cryptographic purposes is known as a: a) hash b) private key c) public key d) cipher
d) cipher
DES, IDEA, RC4, and WPA are examples of: a) key revocation b) 802.11b wireless security c) asymmetric key algorithms (or standards) d) symmetric algorithms (or standards)
d) symmetric algorithms (or standards)
Which of the following is one of the four basic forms of a cryptographic attack? a) ciphertext-only attack b) Known-plaintext attack c) Chosen-plaintext attack d) Chosen-ciphertext attack e) All of these are correct.
e) All of these are correct.
Bob is sending a message to Alice. He wants to ensure that nobody can read the content of the message while it is in transit. What goal of cryptography is Bob attempting to achieve? a) Integrity b) Confidentiality c) Authentication d) Nonrepudiation
b) Confidentiality Confidentiality keeps information secret from unauthorized users. Cryptography makes information unintelligible to anyone who does not know the encryption cipher and the proper key. Only authorized users, or an effective cryptanalysis, can decipher the content of an encrypted message.
What is not a symmetric encryption algorithm? a) Data Encryption Standard (DES) b) Diffie-Hellman c) International Data Encryption Algorithm (IDEA) d) Carlisle Adams Stafford Tavares (CAST)
b) Diffie-Hellman DES, CAST, and IDEA are all symmetric algorithms. Diffie-Hellman is an asymmetric algorithm.
Which of the following is not true of hash functions? a) The hashes produced by a specific hash function may vary in size. b) The output from the message digest algorithm (MD5) or the Secure Hash Algorithm (SHA) hash provides input for an asymmetric key algorithm that uses a private key as input. c) Hash functions help detect forgeries by computing a checksum of a message and then combining it with a cryptographic function so that the result is tamperproof. d) A hash is a checksum designed so that no one can forge a message in a way that will result in the same hash as a legitimate message.
a) The hashes produced by a specific hash function may vary in size. Hashes are usually of a known fixed size based on the algorithm used.
Which type of cipher works by rearranging the characters in a message? a) Transposition b) Asymmetric c) Substitution d) Steganographic
a) Transposition A transposition cipher does not alter the characters in a message. Instead, it rearranges them using a complex pattern and requires that the receiver unscramble them following the reverse pattern.
Alice and Bob would like to communicate with each other using a session key, but they do not already have a shared secret key. Which algorithm can they use to exchange a secret key? a) Blowfish b) Diffie-Hellman c) Message digest algorithm (MD5) d) Rivest-Shamir-Adelman (RSA)
b) Diffie-Hellman Using the Diffie-Hellman algorithm, the sender and receiver use asymmetric encryption to securely exchange symmetric keys. After the initial key exchange, each party can then use symmetric encryption to encrypt and decrypt data.
Juan is a wireless security professional. He is selecting a standard for wireless encryption protocols for access points and devices for his agency. For the highest security, which protocol should Juan choose? a) Wi-Fi Protected Access version 2 (WPA2) b) Wi-Fi Protected Access version 3 (WPA3) c) Wi-Fi Protected Access (WPA) d) Wired Equivalent Privacy (WEP)
b) Wi-Fi Protected Access version 3 (WPA3) The WEP algorithm is cryptographically insecure and should no longer be used. WPA and its successor WPA2 are both strong, secure wireless encryption protocols. WPA3 is the newest and most secure protocol of the four listed here.
What is the only unbreakable cipher when it is used properly? a) Blowfish b) Rivest-Shamir-Adelman (RSA) c) Vernam d) Elliptic Curve Diffie-Hellman Ephemeral (ECDHE)
c) Vernam The Vernam cipher, also known as a one-time pad, is unbreakable provided that the key is at least as long as the message and that each key is only used one time.
