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Course Description

Credit Units: 2

Lecturer: Mr. Akuwudike Eze (MCs; NCSA, NIIT), Email: Social Learning Tool:, Journals:,  College of Agriculture, Engineering and Environmental Design, Department of Computer Science & Cyber Security.

Course Description:

Cryptography is defined as: “The enciphering and deciphering of messages in secret code or cipher.” However, cryptography today is a much broader field; it aims to protect honest parties from malicious parties. For example, malicious parties can eavesdrop to the communication on the Internet and try to read messages sent by other parties; they can try to impersonate other parties, or login to computers without permission. Basic topics in cryptography are secure encryption, digital signatures, and fault-tolerant protocols. The course will cover these topics, their realizations, and applications.

The modern study of cryptography investigates techniques for facilitating interactions between distrustful entities. In our connected society, such techniques have become indispensable—enabling, for instance, automated teller machines, secure wireless networks, internet banking, satellite radio/television and more.

In this course we introduce some of the fundamental concepts of this study. Emphasis will be placed on the foundations of cryptography and in particular on precise definitions and proof techniques.

Course Objectives:

1. Classical cryptosystems

We will cover only a small selection of classical (paper-and-pencil) cryptosystems, including substitution and transposition (permutation) ciphers as Vigènere. You should know how these work and how to cryptanalyse them. Among tools here you should know how to make use of mono-, bi- and n-gram frequencies, the Kasiski test and coincidence index.

You should also know the principles behind rotor machines such as Enigma and have an understanding of the importance of these machines and their cryptanalysis during World War II.

This material is covered in Chapter 2 of the course book. There is also a large number of web sites devoted to these topics, easily found by Google search.

2. Stream ciphers

In this brief part we discuss Linear Feedback Shift Registers as a way of implementing stream ciphers and analyze their properties and give some examples. We also discuss RC4. Stream ciphers are discussed in chapter 7, but LFSR’s are not mentioned.

3. Cryptographic Protocols

Cryptographic primitives need to be embedded in protocols in order to provide useful services. We will discuss a number of such services as examples; in particular protocols for key management and identification. We will also discuss some examples of broken protocols. Book reference: chapters 14 and 15.

4. Information theory

We will briefly discuss probabilistic models of encryption and Shannon’s notion of perfect security. We discuss Shannon’s bound on key length for perfect security and show that the one-time pad achieves this. We introduce the notion of entropy and redundancy of a language and show how the redundancy of the plaintext language affects the amount of ciphertext that is needed for unique decryption.

Recommended Textbooks

  • Introduction to Modern Cryptography – Katz and Lindell – ISBN: 978-1584885511
  • Stallings: Cryptography and Network Security, 5th ed., ISBN 0-13-705632-x

Methods of Course Assessment:

Evaluation will be carried out in accordance with the university policy. The lecturer will present a written course outline with specific evaluation criteria at the beginning of the semester. Evaluation will be based on the following:

Criteria Marks

Class Tests 15

Class Assignments 15

Final Examination 70


Pre-requisite courses:


Co-requisite course(s):


Recommended Reference Materials:


  1. Cyberspace, Cybersecurity, and Cybercrime (NULL) 1st Edition by Janine Kremling (Author), Amanda M. Sharp Parker



Please click on the course content tab to have access to all required materials for this course.

Legacy University COVID-19 Response

We wish you and your loved ones health and peace during these uncharted times. Our University remains open with the implementation of online classes for the 2020 academic year via our Legacy University Open eSchool (

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