LAB 3 - Classic cryptography

During this lab, we will implement the Caesar Cipher and Vigenere Cipher for Symmetric Cryptography.

As in the previous lecture, we already know that cryptography is divided into 2 main categories which is symmetric and asymmetric. In symmetric encipherment, plaintext is encrypted and decrypts using the same key whereas asymmetric encipherment is using different keys to encrypt and decrypt a plaintext.


Below is an example of symmetric encipherment using Caesar Cipher

The Caesar Cipher is formed by shifting the letters of the original alphabet. For example by replacing each letter of the alphabet with the letter three places down the alphabet. It is monoalphabetic as only one letter in plaintext is exchanged for one letter of ciphertext.

Plaintext alphabet A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Ciphertext key D E F G H I J KLM NO P Q RS T U V W X Y Z A B C

A caesar cipher with a key 3

For an example the plain text below can be encrypted using key 3 to get the cipher text

THE ATTACK TONIGHT START AT EIGHT, REGROUP AT STATION A

Plaintext

WKHDWWDFNWRQLJKWVWDUWDWHLJKWUHJURXSDWVWDWLRQD

Ciphertext

Example of symmetric cryptography using Vigenere Cipher

Vigenere table

The cipher text encrypted using Caesar cipher method is easily broken by using a brute force attack. An attacker can easily try every combinations of character to break the code as the number of possibility is just 26. In order to improve the deciphering process we can used the vigeneré cipher method. The Vigenère cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. It is a simple form of polyalphabetic substitution. You can refer to the Vigenere table for making it easier to encrypt a plaintext using this method.

A key is needed to encrypt a plaintext; a key can be a word or a phrase. To have a strong cipher text it is advised to use different key on each encryption. This will prevent from a brute force attack on a second message if the first message has been intercepted.

Vigenere Cipher

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LECTURE 3: Modern cryptography

The topic covered in this lecture are:

• Modern cryptography algorithm
• Block and stream
• DES
• AES
• MAC
• Digital Signature, RSA

DES
* Provides a high level of security
* The security depends on keys, not the secrecy of the algorithm
* The security is capable of being evaluated
* The algorithm is completely specified and easy to understand
* It is efficient to use and adaptable
* Must be available to all users
* Must be exportable

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LAB 2 - The goals of information technology security

During this lab, we need to do 4 tasks which is:

Task 1-Using NTFS to Secure Local Resources
Task 2- Data Confidentiality
Task 3- Data Availibility
Task 4- Data Integrity

Basically, in this lab we learn how to determine if the partition is NTFS or FAT32. Besides that, we also learn how to implement confidentiality, availability and integrity in Windows Server 2003.

TASK 1- Using NTFS to Secure Local Resources.

1. Open your winserv03 virtual machine
2. Log on to the Windows 2003 server as Administrator.
3. Click [Start].
4. Click [Run].
5. Type cmd to invoke the command line. (The FAT partition in
this lab will be designated as drive letter D.)
6. At the command line type chkntfs d: to verify that the drive
is not using NTFS. You will see the m7. To convert a FAT disk to NTFS you need to type at the
command line convert d: /fs:ntfs
7. If the drive has a volume label, enter it when prompted.
Windows will then convert the drive to NTFS. Note: If you
convert the system partition you will have to reboot for the
conversion to take place.
8. At the command line type chkntfs d: to verify that the drive
is now NTFS.essage, “D: is not
9. Close all Windows and log off.

TASK 2::Data Confidentiality.

Once a secure file system is installed, you can begin to think about
data confidentiality. Data confidentiality refers to making sure that
only those intended to have access to certain data actually have
that access. With the FAT file system, this is not possible at the
local level, but with NTFS you can lock down both folders and files
locally. NTFS can be used to protect data from intruders who may
have physical access to the computer containing the data. In this
lab, you will create a folder and files, assign NTFS permissions,
then verify whether or not the data is confidential.

Creating user account
1. Two user-level accounts: User1 and User2
a. To create user account go to [Start] |
[Administrative Tools] | [Computer Management].
b. Choose [Local User and Groups] and double click
on the [user] folder.
c. To create new user right click on the pane and from
the pop-up menu choose [New User] and fill up the
necessary information such as username and
password (use easy to remember password e.g.
abc123)

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