CH 2

Question 1

….. is the cornerstone of computer

and communications security.

Answer 1

Modern cryptography.

Question 2

Its foundation is based on various concepts of mathematics such as:

Answer 2

• number theory,
• computational-complexity theory,
• probability theory.

Question 3

How does Classic cryptography manipulate ?

Answer 3

Classic Cryptography manipulates traditional characters.

Question 4

How does Modern cryptography manipulate ?

Answer 4

Modern Cryptography operates on binary bit sequences.

Question 5

What is Classic cryptography based on ?

Answer 5

Classic Cryptography is mainly based on ‘security through obscurity’. the techniques employed for coding were kept secret and only the parties involved in communication knew about them.

Question 6

What is Modern cryptography based on ?

Answer 6

• Modern Cryptography relies on publicly known mathematical algorithms for coding the information. Secrecy is obtained through a secret key which is used as the seed for the algorithms. The computational difficulty of algorithms and absence of secret key makes it impossible for an attacker to obtain the original information even if he knows the algorithm used for coding.

Question 7

What does Classic cryptography require ?

Answer 7

It requires the entire cryptosystem for communicating confidentially.

Question 8

What does Modern cryptography require ?

Answer 8

it requires parties interested in secure communication to possess the secret key only.

Question 9

Cryptology consists of 2 important thing ….. and ….. .

Answer 9

Cryptography, Cryptoanalysis.

Question 10

What is cryptography ?

Answer 10

it is the art and science of making a cryptosystem that is capable of providing information security. Cryptography deals with the actual securing of digital data. It refers to the design of mechanisms based on mathematical algorithms that provide fundamental information security services.

Question 11

We can look at cryptography as a large toolkit containing ….. .

Answer 11

Different techniques in security applications.

Question 12

What is Cryptanalysis?

Answer 12

It is the art and science of breaking the cipher text. It involves the study of cryptographic mechanism with the intention to break them.

Question 13

Cryptanalysis is also used during the design of the new cryptographic techniques to ….. .

Answer 13

Test their security strengths.

Question 14

….. is concerned with the design of cryptosystems while ….. studies the breaking of the cryptosystems.

Answer 14

Cryptography, Cryptoanalysis.

Question 15

What are the 4 primary objects of Cryptography ?

Answer 15

• Confidentiality
• Data Integrity
• Authentication
• Non-repudiation

Question 16

Define Confidentiality.

Answer 16

Confidentiality is the fundamental security service provided by cryptography. It is a security service that keeps the information from an unauthorized person. It is sometimes referred to as privacy or secrecy.

Question 17

How can confidentiality be achieved ?

Answer 17

Confidentiality can be achieved through numerous means starting from physical securing to the use of mathematical algorithms for data encryption.

Question 18

Define Data integrity.

Answer 18

It is security service that deals with identifying any alteration to the data. The data may get modified by an unauthorized entity intentionally or accidently. Integrity service confirms that whether data is intact or not since it was last created, transmitted, or stored by an authorized user.

Question 19

Can data integrity prevent the alteration of data ?

Answer 19

NO, But it provides the means for detecting whether data has been manipulated in an unauthorized manner.

Question 20

Define Authentication.

Answer 20

It provides the identification of the originator. It confirms to the receiver that the data received has been sent only by an identified and verified sender.

Question 21

What are the 2 variants of authentication service ?

Answer 21

• Message authentication identifies the originator of the message without any regard router or system that has sent the message.
• Entity authentication is assurance that data has been received from a specific entity, say a
  particular website.

Question 22

Define Non-repudiation.

Answer 22

It is a security service that ensures that an entity cannot refuse the ownership of a previous commitment or an action. It is an assurance that the original creator of the data cannot deny the creation or transmission of the said data to a recipient or third
party.

Question 23

….. is a property that is most desirable in situations

where there are chances of a dispute over the exchange of data.

Answer 23

Non-repudiation.

Question 24

Define cryptography primitives.

Answer 24

Cryptography primitives are the tools and techniques in Cryptography that can be selectively used to provide a set of desired security services.

Question 25

What are the 4 cryptography primitives ?

Answer 25

• Encryption
• Hash functions
• Message Authentication codes (MAC)
• Digital Signatures