CHAPTER 12
Cryptographic Hash Functions
(Solution to Practice Set)
Review Questions
1. A cryptographic hash function takes a message of arbitrary length and creates a
message digest of fixed length.
2. An iterated cryptographic hash function uses a compre

CHAPTER 13
Digital Signature
(Solution to Practice Set)
Review Questions
1. We mentioned four areas in which there is a differences between a conventional
and a digital signature: inclusion, verification, document-signature relation, and
duplicity.
a. Inc

CHAPTER 16
PGP and S/MIME
(Solution to Practice Set)
Review Questions
1. Alice needs to include the identifiers of the algorithms in the packets sent to Bob.
Each packet type has a field that defines the identity of the algorithm being used.
2. Alice need

CHAPTER 11
Message Integrity and
Message Authentication
(Solution to Practice Set)
Review Questions
1. Message integrity guarantees that the message has not been changed. Message
authentication guarantees that the sender of the message is authentic.
2. Th

CHAPTER 18
IPSec
(Solution to Practice Set)
Review Questions
1. IPSec operates in one of the two modes: the transport mode or tunnel mode.
a. In the transport mode, IPSec protects what is delivered from the transport layer
to the network layer. In other w

CHAPTER 14
Entity Authentication
(Solution to Practice Set)
Review Questions
1. There are two differences between message authentication and entity authentication. First, message authentication might not happen in real time; entity authentication does. Se

CHAPTER 15
Key Management
(Solution to Practice Set)
Review Questions
1. The following shows the main duties.
a. KDC establishes a shared secret key between itself and each newly joined
member.
b. KDC accepts requests from members who wants to establish a

CHAPTER 17
SSL and TLS
(Solution to Practice Set)
Review Questions
1. Five services are provided by SSL or TLS: fragmentation, compression, message
integrity, confidentiality, and framing. SSL or TLS
2. In SSL, a 48-byte master secret is created from the

CHAPTER 2
Mathematics of Cryptography
Part I
(Solution to Practice Set)
Review Questions
1. The set of integers is Z. It contains all integral numbers from negative infinity to
positive infinity. The set of residues modulo n is Zn. It contains integers fr

CHAPTER 5
Introduction to Modern
Symmetric-Key Ciphers
(Solution to Practice Set)
Review Questions
1. The traditional symmetric-key ciphers are character-oriented ciphers. The modern
symmetric-key ciphers are bit-oriented ciphers.
2. To be resistant to ex

CHAPTER 4
Mathematics of Cryptography
Part II: Algebraic Structures
(Solution to Practice Set)
Review Questions
1. The combination of the set and the operations that are applied to the elements of
the set is called an algebraic structure. We have defined

CHAPTER 3
Traditional Symmetric-Key
Ciphers
(Solution to Practice Set)
Review Questions
1. Symmetric-key encipherment uses a single key for both encryption and decryption. In addition, the encryption and decryption algorithms are inverse of each
other.
2.

CHAPTER 6
Data Encryption Standard (DES)
(Solution to Practice Set)
Review Questions
1. The block size in DES is 64 bits. The cipher key size is 56 bits. The round key size
is 48 bits.
2. DES uses 16 rounds.
3. In the first approach, DES uses 16 mixers an

CHAPTER 1
Introduction
(Solution to Practice Set)
Review Questions
1. The three security goals are confidentiality, integrity, and availability.
Confidentiality means protecting confidential information.
Integrity means that changes to the information n

CHAPTER 7
AES
(Solution to Practice Set)
Review Questions
1. The criteria defined by NIST for selecting AES fall into three areas: security, cost,
and implementation.
2. The following table lists the parameters:
Version
Block
size
Key
size
Round-key size

CHAPTER 8
Encipherment Using Modern
Block Ciphers
(Solution to Practice Set)
Review Questions
1. Modern block ciphers encrypt and decrypt small blocks. DES uses a block size of
8 bytes (characters) and AES uses a block size of 16 bytes (characters). In re

CHAPTER 10
Symmetric-Key Cryptography
(Solution to Practice Set)
Review Questions
1. Symmetric-key cryptography is based on sharing secrecy; asymmetric-key cryptography is based on personal secrecy.
2. In asymmetric-key cryptography, each entity has a pai

CHAPTER 9
Mathematics of Cryptography: Part 3
(Solution to Practice Set)
Review Questions
1. A positive integer is a prime if and only if it is exactly divisible by two integers, 1
and itself. A composite is a positive integer with more than two divisors.