Chapter 7
Conden.ality Using
Symmetric Encryp.on
Conden.ality using Symmetric Encryp.on
tradi.onally symmetric encryp.on is used to
provide message conden.ality
Conden.ality using Symmetric Encryp.on
Poten.al loca.on

EECE 632 Cryptography and Computer Security
Suggested Exercises
CHAPTER 2
Exercise 1
A generalization of the Caesar Cipher is the Affine Cipher given by: C = (a.P + b) mod 26,
Where P is the plain character and C is the cipher character after encryption,

EECE 632 Cryptography and Computer Security
Question [8.3]
Let n be an integer and p be a prime number. Explain why for all such n and p:
gcd(n, n+p) = 1 or p
Question [8.4]
Using Fermat Theorem, find 5
301
mod 11.
Question [8.6]
Use Fermat Theorem to fin

EECE 632 Cryptography and Computer Security
Question [8.3]
Let n be an integer and p be a prime number. Explain why for all such n and p:
gcd(n, n+p) = 1 or p
Question [8.4]
Using Fermat Theorem, find 5
301
mod 11.
Question [8.6]
Use Fermat Theorem to fin

EECE 632 Cryptography and Computer Security
Suggested Exercises
CHAPTER 3
Exercise 1
Compute the bits numbered 5, 35, 40, and 55 at the output of the first round of DES decryption,
assuming that the ciphertext block is composed only of ones and the extern

SET #1 Solution
Exercise 1:
a) H = 7
C = (5*7+9) mod 26 = 44 mod 26 = 18 => letter S
I = 8
C = (5*8+9) mod26 = 65 mod 26 = 23 => letter X
Cipher text: SX.
b) a-1 is the inverse of 5 mod 2

Department of Electrical and Computer
Engineering
EECE 632: Cryptography and Computer
Security
Homework 1
Prepared for:
Prof. Ali Chehab
Submitted by:
Emilie Akiki
Linda Fayad
Farouk Ziad Moukaddem
Problem 1:
a) We have C=(a.P +b) mod 26 where a=5 and b

Chapter 14
Authentication Applications
Authentication Applications
will consider authentication functions
developed to support application-level
authentication & digital signatures
will consider Kerberos a private-key
authentication service
then X.509

Chapter 13
Digital Signatures & Authentication
Protocols
Digital Signatures
Message authentication protects two parties
from a third party but it does not protect
them against each other:
Alice may forge a different message and claim that
it came from B

Chapter 2
Classical Encryp1on
Techniques
Symmetric Encryp1on
or conven1onal / private-key / single-key
sender and recipient share a common key
all classical encryp1on algorithms are private-
key
was only type p

Chapter 6
Contemporary Symmetric Ciphers
Mul5ple Encryp5on & DES
clear a replacement for DES was needed
theore5cal a<acks that can break it
demonstrated exhaus5ve key search a<acks
AES is a new cipher alterna

Chapter 8
Introduc0on to Number Theory
Prime Numbers
prime numbers only have divisors of 1 and self
they cannot be wri>en as a product of other numbers
note: 1 is prime, but is generally not of interest

Chapter 9
Public Key Cryptography and RSA
Chapter 9 Public Key Cryptography and RSA
Every Egyp)an received two names, which were known
respec)vely as the true name and the good name, or
the great name and

Chapter 10
Key Management
Other Public Key Cryptosystems
Key Management
public-key encryp<on helps address key
distribu<on problems
have two aspects of this:
distribu<on of public keys
use of public-key enc

Chapter 11
Message Authen0ca0on and
Hash Func0ons
Message Authen0ca0on
message authen0ca0on is concerned with:
protec0ng the integrity of a message
valida0ng iden0ty of originator
non-repudia0on of origin (

Chapter 5
Advanced Encryp1on Standard
"It seems very simple."
"It is very simple. But if you don't know what the
key is it's virtually indecipherable."
Talking to Strange Men, Ruth Rendell
Origins
clear a repla

VPN and IPsec
Networking Security and Cryptography
Prepared by:
Miriana Itani
Malakeh Karaouni
Presented to: Dr. Kassem Ahmad
S
Y
L
L
A
B
U
S
VPN Importance
Advantages and Disadvantages
VPN Configurations and Categories
Security (IPsec)
VPN Importance
I a