Chapter 1

Question 1

What are the three security goals?

Answer 1

Confidentiality, Integrity, Availability

Question 2

What are security attacks?

Answer 2

Threats that compromise the three security goals

Question 3

What are security services?

Answer 3

Mechanisms implemented to achieve security goals

Question 4

What are security mechanisms?

Answer 4

Tools or processes used to provide security services

Question 5

What two techniques are introduced to implement security mechanisms?

Answer 5

Cryptography, Steganography

Question 6

Define computer security according to NIST.

Answer 6

Protection of an automated information system to preserve integrity, availability, and confidentiality

Question 7

What are the three fundamental questions in computer security?

Answer 7

• What assets do we need to protect? * How are those assets threatened? * What can we do to counter those threats?

Question 8

What does network security refer to?

Answer 8

Measures to protect data during transmission and to prevent unauthorized access

Question 9

What is Internet security?

Answer 9

Protection of data during transmission over interconnected networks

Question 10

True or False: Nothing is ever completely or truly secure.

Answer 10

True

Question 11

What is the CIA triad?

Answer 11

Confidentiality, Integrity, Availability

Question 12

What does confidentiality mean in information security?

Answer 12

Protection of confidential information from unauthorized access

Question 13

What does integrity mean in the context of information?

Answer 13

Changes to information must be made only by authorized entities

Question 14

What does availability signify in information security?

Answer 14

Information must be accessible to authorized entities

Question 15

What is snooping?

Answer 15

Unauthorized access to or interception of data

Question 16

Define modification in the context of security attacks.

Answer 16

Interception and alteration of a message by an attacker

Question 17

What is masquerading or spoofing?

Answer 17

When an attacker impersonates someone else

Question 18

What does replaying mean in security attacks?

Answer 18

Obtaining a copy of a message and re-sending it

Question 19

What is repudiation in security context?

Answer 19

Sender or receiver denies having sent or received a message

Question 20

What is a denial of service (DoS) attack?

Answer 20

An attack that slows down or interrupts service

Question 21

What does ITU-T provide in terms of security?

Answer 21

Security services and mechanisms

Question 22

What is cryptography?

Answer 22

The science and art of transforming messages to secure them

Question 23

What does the term steganography mean?

Answer 23

Covered writing, in contrast to secret writing

Question 24

What is encryption?

Answer 24

Transformation of intelligible information into unintelligible form

Question 25

What is decryption?

Answer 25

Transformation of encrypted information back into intelligible form

Question 26

What is cryptanalysis?

Answer 26

Analyzing encrypted information to recover the original message

Question 27

What is cryptology?

Answer 27

The field encompassing both cryptography and cryptanalysis

Question 28

What is the study of principles and methods of deciphering ciphertext without knowing the key called?

Answer 28

Cryptology ## Footnote Cryptology encompasses both cryptography and cryptanalysis.

Question 29

What is the original message before encryption called?

Answer 29

Plain text

Question 30

What is the algorithm used to transform plaintext into unintelligible form called?

Answer 30

Encryption Algorithm

Question 31

What is the encrypted text referred to as?

Answer 31

Cipher text

Question 32

What is the key used in the encryption process called?

Answer 32

Encryption key

Question 33

What is the algorithm used to transform cipher text back to plaintext called?

Answer 33

Decryption Algorithm

Question 34

What is the key used in the decryption process called?

Answer 34

Decryption key

Question 35

In a cryptosystem, what must be public while the keys remain secret?

Answer 35

All algorithms

Question 36

What type of intruder listens to communications without modification?

Answer 36

Passive intruder

Question 37

What type of intruder modifies messages and re-inserts them?

Answer 37

Active intruder

Question 38

What does cryptography ensure regarding the knowledge of transferred information?

Answer 38

Confidentiality

Question 39

What does cryptography ensure regarding the integrity of a message during transmission?

Answer 39

Integrity

Question 40

What does authenticity in cryptography confirm?

Answer 40

You can verify that you are talking to the entity you think you are talking to

Question 41

What does identity in cryptography allow you to verify?

Answer 41

Who is the specific individual behind that entity

Question 42

What does non-repudiation ensure in cryptography?

Answer 42

The individual behind that asset cannot deny being associated with it

Question 43

What is the classification of cryptography based on the number of keys used?

Answer 43

Symmetric key cryptography and Asymmetric key cryptography

Question 44

What type of cryptography uses the same key for encryption and decryption?

Answer 44

Symmetric key cryptography

Question 45

What type of cryptography uses two mathematically related keys?

Answer 45

Asymmetric key cryptography

Question 46

What is an example of symmetric encryption?

Answer 46

DES (Data Encryption Standard)

Question 47

What must both sender and receiver possess in a symmetric encryption system?

Answer 47

The same key

Question 48

What are two requirements for secure use of symmetric encryption?

Answer 48

A strong encryption algorithm and a secret key known only to sender/receiver

Question 49

What is the mathematical representation of encryption in symmetric cryptography?

Answer 49

C = E_K(M)

Question 50

What is the mathematical representation of decryption in symmetric cryptography?

Answer 50

M = D_K(C)

Question 51

What is a substitution cipher?

Answer 51

Replaces the actual bits, character, or block of characters with substitutes

Question 52

What is a transposition cipher?

Answer 52

Rearranges the order of the bits, characters, or blocks of characters

Question 53

What is a product cipher?

Answer 53

Combination between transposition cipher and substitution cipher

Question 54

What is a key characteristic of asymmetric key cryptography?

Answer 54

The relation between the two keys is unknown

Question 55

What can messages encrypted with the public key be decrypted with?

Answer 55

The private key

Question 56

What can messages encrypted with the private key be decrypted with?

Answer 56

The public key

Question 57

What are the essential steps in the asymmetric encryption model?

Answer 57

* Each entity generates a pair of keys * Each entity publishes its public key * User A encrypts a message using User B's public key * User B decrypts the message using their private key

Question 58

What are examples of asymmetric ciphers?

Answer 58

* RSA * Rabin * ElGamal * Elliptic curve cryptography

Question 59

What is a digital signature?

Answer 59

Data appended to, or a cryptographic transformation of, a data unit that allows a recipient to prove the source and integrity of the data unit

Question 60

What are the two fundamental assumptions upon which digital signatures depend?

Answer 60

* The private key is secure * The only way to produce a digital signature is to use the private key

Question 61

What must a digital signature be verifiable by?

Answer 61

Third parties to resolve disputes

Question 62

What must be possible to verify regarding a digital signature?

Answer 62

* The author * The date * The time

Question 63

What is a key property of digital signatures?

Answer 63

The signature must be verifiable by third parties to resolve disputes. ## Footnote This ensures that the authenticity of the signature can be confirmed by someone other than the signer.

Question 64

What must be possible to verify regarding a digital signature?

Answer 64

The author, the date, and time of the signature. ## Footnote This verification is crucial for establishing the context and legitimacy of the signature.

Question 65

What must be authenticated at the time of a digital signature?

Answer 65

The contents. ## Footnote This ensures that the information being signed has not been altered after the signature was created.

Question 66

Name one standard associated with digital signatures.

Answer 66

DSS (Digital Signature Standard). ## Footnote DSS is a federal information processing standard for digital signatures.

Question 67

What is one example of a digital signature algorithm?

Answer 67

RSA (Rivest-Shamir-Adleman). ## Footnote RSA is widely used for secure data transmission.

Question 68

What is a key advantage of symmetric-key cryptography?

Answer 68

High rates of data throughput. ## Footnote This allows for faster encryption and decryption processes compared to asymmetric-key methods.

Question 69

What is a disadvantage of symmetric-key cryptography?

Answer 69

The key must remain secret in two-party communication. ## Footnote This requirement complicates the secure exchange of keys between parties.

Question 70

What challenge arises in large networks with symmetric-key cryptography?

Answer 70

Many key pairs must be managed. ## Footnote This leads to a significant increase in the number of keys required as the number of users grows.

Question 71

How many keys does a cryptosystem with n users require?

Answer 71

n*(n-1)/2 keys. ## Footnote This formula arises from the need for each user to have a unique key with every other user.

Question 72

What is a key advantage of asymmetric-key cryptography?

Answer 72

Only the private key must be kept secret. ## Footnote This simplifies key management since the public key can be shared openly.

Question 73

What problem does asymmetric-key cryptography aim to solve?

Answer 73

Key distribution and digital signature. ## Footnote These issues are critical in ensuring secure communications and verifying identities.

Question 74

What is a disadvantage of asymmetric-key cryptography?

Answer 74

Slower than the best-known symmetric key schemes. ## Footnote The computational complexity of asymmetric algorithms leads to longer processing times.

Question 75

What is typically larger in asymmetric-key cryptography compared to symmetric-key cryptography?

Answer 75

Key sizes. ## Footnote Larger key sizes are necessary to achieve comparable security levels.