SOLUTIONS MANUAL
CRYPTOGRAPHY AND NETWORK SECURITY: PRINCIPLES
AND PRACTICE
8TH EDITION
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.
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 protection of network devices, such as routers and switches, and
end systems connected to the network, such as client systems and servers.
,1.7 Trust: The willingness of a party to be vulnerable to the actions of another party 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 confidentiality is low, the
potential impact from a loss of integrity is low, and the potential impact from a loss of
availability is low.
d. The management within the contracting organization determines that: (i) for the sensitive
contract information, the potential impact from a loss of confidentiality is moderate, the potential
impact from a loss of integrity is moderate, and the potential impact from a loss of availability is
low; and (ii) for the routine administrative information
(non-privacy-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.)
CRYPTOGRAPHY AND NETWORK SECURITY: PRINCIPLES
AND PRACTICE
8TH EDITION
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.
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 protection of network devices, such as routers and switches, and
end systems connected to the network, such as client systems and servers.
,1.7 Trust: The willingness of a party to be vulnerable to the actions of another party 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 confidentiality is low, the
potential impact from a loss of integrity is low, and the potential impact from a loss of
availability is low.
d. The management within the contracting organization determines that: (i) for the sensitive
contract information, the potential impact from a loss of confidentiality is moderate, the potential
impact from a loss of integrity is moderate, and the potential impact from a loss of availability is
low; and (ii) for the routine administrative information
(non-privacy-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.)
