SOLUTIONS MANUAL
CRYPTOGRAPHY AND
NETWORK SECURITY:
PRINCIPLES AND PRACTICE
EIGHTH EDITION
TABLE OF CONTENTS
CHAPTERS 1–10
Chapter 1 Introduction ............................................................... 5
Chapter 2 Introduction to Number Theory .................................... 8
Chapter 3 Classical Encryption Techniques ................................. 16
Chapter 4 Block Ciphers and the Data Encryption Standard .......... 25
Chapter 5 Finite Fields ............................................................. 35
Chapter 6 Advanced Encryption Standard ................................... 41
Chapter 7 Block Cipher Operation .............................................. 48
Chapter 8 Random and Pseudorandom Number Generation and
Stream Ciphers ........................................................................ 54
Chapter 9 Public-Key Cryptography and RSA .............................. 62
Chapter 10 Other Public-Key Cryptosystems ............................... 70
, CHAPTER 1 INTRODUCTION
ANSWERS TO QUESTIONS
1.1 The OSI Security Architecture is a framework that provides a systematic
way of defining the requirements for security and characterizing the
approaches to satisfying those requirements. The document defines
security attacks, mechanisms, and services, and the relationships
among these categories.
1.2 Passive attacks: release of message contents and traffic analysis.
Active attacks: masquerade, replay, modification of messages, and
denial of service.
1.3 Authentication: The assurance that the communicating entity is the
one that it claims to be.
Access control: The prevention of unauthorized use of a resource (i.e.,
this service controls who can have access to a resource, under what
conditions access can occur, and what those accessing the resource are
allowed to do).
Data confidentiality: The protection of data from unauthorized
disclosure.
Data integrity: The assurance that data received are exactly as sent by
an authorized entity (i.e., contain no modification, insertion, deletion, or
replay).
Nonrepudiation: Provides protection against denial by one of the entities
involved in a communication of having participated in all or part of the
communication.
Availability service: The property of a system or a system resource
being accessible and usable upon demand by an authorized system
entity, according to performance specifications for the system (i.e., a
system is available if it provides services according to the system design
whenever users request them).
1.4 Cryptographic algorithms: Transform data between plaintext and
ciphertext.
Data integrity: Mechanisms used to assure the integrity of a data unit or
stream of data units.
Digital signature: Data appended to, or a cryptographic transformation
of, a data unit that allows a recipient of the data unit to prove the source
and integrity of the data unit and protect against forgery.
Authentication exchange: A mechanism intended to ensure the identity
of an entity by means of information exchange.
, lOMoARcPSD|64668135
Traffic padding: The insertion of bits into gaps in a data stream to
frustrate traffic analysis attempts.
Routing control: Enables selection of particular physically or logically
secure routes for certain data and allows routing changes, especially
when a breach of security is suspected.
Notarization: The use of a trusted third party to assure certain
properties of a data exchange.
Access control: A variety of mechanisms that enforce access rights to
resources.
1.5 Keyless: Do not use any keys during cryptographic transformations.
Single-key: The result of a transformation are a function of the input
data and a single key, known as a secret key.
Two-key: At various stages of the calculate two different but related
keys are used, referred to as private key and public key.
1.6 Communications security: Deals with the protection of
communications through the network, including measures to protect
against both passive and active attacks.
Device security: Deals with the pr
based on the expectation that the other will perform a particular action
important to the trustor, irrespective of the ability to monitor or control
that other party.
Trustworthiness: A characteristic of an entity that reflects the degree
to which that entity is deserving of trust.
ANSWERS TO PROBLEMS
1.1 The system must keep personal identification numbers confidential, both
in the host system and during transmission for a transaction. It must
protect the integrity of account records and of individual transactions.
Availability of the host system is important to the economic well being of
the bank, but not to its fiduciary responsibility. The availability of
individual teller machines is of less concern.
1.2 The system does not have high requirements for integrity on individual
transactions, as lasting damage will not be incurred by occasionally
losing a call or billing record. The integrity of control programs and
configuration records, however, is critical. Without these, the switching
function would be defeated and the most important attribute of all -
availability - would be compromised. A telephone switching system must
also preserve the confidentiality of individual calls, preventing one caller
from overhearing another.
, 1.3 a. The system will have to assure confidentiality if it is being used to
publish corporate proprietary material.
b. The system will have to assure integrity if it is being used to laws or
regulations.
c. The system will have to assure availability if it is being used to publish a
daily paper.
1.4 a. An organization managing public information on its web server
determines that there is no potential impact from a loss of
confidentiality (i.e., confidentiality requirements are not applicable), a
moderate potential impact from a loss of integrity, and a moderate
potential impact from a loss of availability.
b. A law enforcement organization managing extremely sensitive
investigative information determines that the potential impact from a loss
of confidentiality is high, the potential impact from a loss of integrity is
moderate, and the potential impact from a loss of availability is moderate.
c. A financial organization managing routine administrative information (not
privacy-related information) determines that the potential impact from a
loss of
d. acy-related information), the potential impact from a loss of
confidentiality is low, the potential impact from a loss of integrity is low,
and the potential impact from a loss of availability is low.
e. The management at the power plant determines that: (i) for the sensor
data being acquired by the SCADA system, there is no potential impact
from a loss of confidentiality, a high potential impact from a loss of
integrity, and a high potential impact from a loss of availability; and (ii)
for the administrative information being processed by the system, there is
a low potential impact from a loss of confidentiality, a low potential
impact from a loss of integrity, and a low potential impact from a loss of
availability. (Examples from FIPS 199.)
CHAPTER 2 INTRODUCTION TO NUMBER
THEORY
ANSWERS TO QUESTIONS
2.1 A nonzero b is a divisor of a if a = mb for some m, where a, b, and m
are integers. That is, b is a divisor of a if there is no remainder on
division.
2.2 It means that b is a divisor of a.
CRYPTOGRAPHY AND
NETWORK SECURITY:
PRINCIPLES AND PRACTICE
EIGHTH EDITION
TABLE OF CONTENTS
CHAPTERS 1–10
Chapter 1 Introduction ............................................................... 5
Chapter 2 Introduction to Number Theory .................................... 8
Chapter 3 Classical Encryption Techniques ................................. 16
Chapter 4 Block Ciphers and the Data Encryption Standard .......... 25
Chapter 5 Finite Fields ............................................................. 35
Chapter 6 Advanced Encryption Standard ................................... 41
Chapter 7 Block Cipher Operation .............................................. 48
Chapter 8 Random and Pseudorandom Number Generation and
Stream Ciphers ........................................................................ 54
Chapter 9 Public-Key Cryptography and RSA .............................. 62
Chapter 10 Other Public-Key Cryptosystems ............................... 70
, CHAPTER 1 INTRODUCTION
ANSWERS TO QUESTIONS
1.1 The OSI Security Architecture is a framework that provides a systematic
way of defining the requirements for security and characterizing the
approaches to satisfying those requirements. The document defines
security attacks, mechanisms, and services, and the relationships
among these categories.
1.2 Passive attacks: release of message contents and traffic analysis.
Active attacks: masquerade, replay, modification of messages, and
denial of service.
1.3 Authentication: The assurance that the communicating entity is the
one that it claims to be.
Access control: The prevention of unauthorized use of a resource (i.e.,
this service controls who can have access to a resource, under what
conditions access can occur, and what those accessing the resource are
allowed to do).
Data confidentiality: The protection of data from unauthorized
disclosure.
Data integrity: The assurance that data received are exactly as sent by
an authorized entity (i.e., contain no modification, insertion, deletion, or
replay).
Nonrepudiation: Provides protection against denial by one of the entities
involved in a communication of having participated in all or part of the
communication.
Availability service: The property of a system or a system resource
being accessible and usable upon demand by an authorized system
entity, according to performance specifications for the system (i.e., a
system is available if it provides services according to the system design
whenever users request them).
1.4 Cryptographic algorithms: Transform data between plaintext and
ciphertext.
Data integrity: Mechanisms used to assure the integrity of a data unit or
stream of data units.
Digital signature: Data appended to, or a cryptographic transformation
of, a data unit that allows a recipient of the data unit to prove the source
and integrity of the data unit and protect against forgery.
Authentication exchange: A mechanism intended to ensure the identity
of an entity by means of information exchange.
, lOMoARcPSD|64668135
Traffic padding: The insertion of bits into gaps in a data stream to
frustrate traffic analysis attempts.
Routing control: Enables selection of particular physically or logically
secure routes for certain data and allows routing changes, especially
when a breach of security is suspected.
Notarization: The use of a trusted third party to assure certain
properties of a data exchange.
Access control: A variety of mechanisms that enforce access rights to
resources.
1.5 Keyless: Do not use any keys during cryptographic transformations.
Single-key: The result of a transformation are a function of the input
data and a single key, known as a secret key.
Two-key: At various stages of the calculate two different but related
keys are used, referred to as private key and public key.
1.6 Communications security: Deals with the protection of
communications through the network, including measures to protect
against both passive and active attacks.
Device security: Deals with the pr
based on the expectation that the other will perform a particular action
important to the trustor, irrespective of the ability to monitor or control
that other party.
Trustworthiness: A characteristic of an entity that reflects the degree
to which that entity is deserving of trust.
ANSWERS TO PROBLEMS
1.1 The system must keep personal identification numbers confidential, both
in the host system and during transmission for a transaction. It must
protect the integrity of account records and of individual transactions.
Availability of the host system is important to the economic well being of
the bank, but not to its fiduciary responsibility. The availability of
individual teller machines is of less concern.
1.2 The system does not have high requirements for integrity on individual
transactions, as lasting damage will not be incurred by occasionally
losing a call or billing record. The integrity of control programs and
configuration records, however, is critical. Without these, the switching
function would be defeated and the most important attribute of all -
availability - would be compromised. A telephone switching system must
also preserve the confidentiality of individual calls, preventing one caller
from overhearing another.
, 1.3 a. The system will have to assure confidentiality if it is being used to
publish corporate proprietary material.
b. The system will have to assure integrity if it is being used to laws or
regulations.
c. The system will have to assure availability if it is being used to publish a
daily paper.
1.4 a. An organization managing public information on its web server
determines that there is no potential impact from a loss of
confidentiality (i.e., confidentiality requirements are not applicable), a
moderate potential impact from a loss of integrity, and a moderate
potential impact from a loss of availability.
b. A law enforcement organization managing extremely sensitive
investigative information determines that the potential impact from a loss
of confidentiality is high, the potential impact from a loss of integrity is
moderate, and the potential impact from a loss of availability is moderate.
c. A financial organization managing routine administrative information (not
privacy-related information) determines that the potential impact from a
loss of
d. acy-related information), the potential impact from a loss of
confidentiality is low, the potential impact from a loss of integrity is low,
and the potential impact from a loss of availability is low.
e. The management at the power plant determines that: (i) for the sensor
data being acquired by the SCADA system, there is no potential impact
from a loss of confidentiality, a high potential impact from a loss of
integrity, and a high potential impact from a loss of availability; and (ii)
for the administrative information being processed by the system, there is
a low potential impact from a loss of confidentiality, a low potential
impact from a loss of integrity, and a low potential impact from a loss of
availability. (Examples from FIPS 199.)
CHAPTER 2 INTRODUCTION TO NUMBER
THEORY
ANSWERS TO QUESTIONS
2.1 A nonzero b is a divisor of a if a = mb for some m, where a, b, and m
are integers. That is, b is a divisor of a if there is no remainder on
division.
2.2 It means that b is a divisor of a.
