Instructions
The concepts covered in this exercise include data structure, OOP, and string manipulation concepts which must be employed to produce Caesar cipher encryption algorithm.
This Lab Ex submission is required. Zero marks will be awarded for non-submission.
• IMPORTANT: Please name your Visual Studio Solution like so (failure to do so will attract a 1% penalty):
– [STUDENT_NO]_[SURNAME]_LabEx2
– (e.g. 222833200_Mhlanga_LabEx2
• PLAGIARISM: Please refer to your Learning Guide as well as the latest University of Johannesburg’s plagiarism policy document entitled: “POLICY: PLAGIARISM”
COPYING: This is an individual assignment; if any copying is detected, all parties involved will score a
0% for the assignment and WILL face disciplinary consequences
Question 1
Background
You are required to write program that will read a file, encrypt the content of the file, and then create a new file that contains the encrypted content.
Your program will make use of the following classes:
Page – This class will be used to represent the content of the file that was read.
PageManager – This class will be used to read page content from and to a file.
APM11A1Encryptor – This class will be used to encrypt the content of a file using the Caesar-Cipher method.
AdvancedAPM11A1Encryptor – This class will be used to encrypt the content of a file using the Exclusive-OR method.
Caesar Cipher
Caesar was a Roman military and political leader during 100BC to 44BC. In order to make the communication channels secure during war, he invented an encryption technique called the Caesar Cipher. The cipher requires a sentence and a key to function properly. Each character in the sentence was then shifted according to the value of the key. Computer programmers adapted the cipher so that it can be used in programs. Each alphabet letter is assigned a value. This value is determined by the position of the letter in the ASCII table. E.g. A=65, B=66, C=67, D=68 …. X=88, Y=89, Z=90. The key is determined by the person who wants to encrypt the sentence. If you select a key=1, and you have a sentence=”TPG11BT is fun”, it will encrypt to: UQH22CU!jt!gvo.
Exclusive-OR Encryption
The exclusive-OR method requires a key and a sentence to function properly. The ACII value of each character in the sentence is exclusive-ORed with the key. E.g. If you select a key=1, and you have a
sentence=”TPG11BT is fun”, it will encrypt to: UQF00CU!hr!gto.
Below is an example of how to exclusive-OR the character in x with 1:
char x = ‘T’; char y = x^1;
NB! Please note that you may not add any additional methods or members to the classes of question 1.1 – 1.4.
1.1. Write a back–end class called Page and save it in a file called Page.cpp. This class must have the following structure:
Private Members
Data
Type Name Description
string cSentences[] This member will store the sentences on the page. You may assume that a record will never have more than 34 sentences.
int cSentenceCounter This member will store the number of sentences on the page.
Public Methods
Return
Type Method Signature Description
Page () A default constructor that will initialise cSentenceCounter to zero.
void addSentence(string sentence) This method will place add a sentence to the Page. You must make use of the cSentences[] array.
string getSentenceAt(int index) This method will retrieve a sentence.
int getNumberOfSentences() This method will return the number of sentences there are on the Page.
1.2. Write a back-end class called PageManager and save it in a file called PageManager.cpp. This class must have the following structure:
Public Methods
Return
Type Method Signature Description
Page loadPageFromFile(string fileName) This method must read the content of the specified file into a Page object and return this Page.
void writePageToFile(string fileName, Page page) This method must write the content of a Page object into the specified file.
1.3. Write a back-end class called APM11A1Encryptor and save it in a file called APM11A1Encryptor.cpp. This class must have the following structure:
Protected Members
Data
Type Name Description
int key This member will store the key that will be used during the encryption process. (You may NOT change the name of this member)
Public Methods
Return
Type Method Signature Description
char encryptACharacter(char character) This method must encrypt the received character by using the key class member and the Caesar Cipher encryption technique.
Page encryptPage(Page page) This method will encrypt the content of the received page parameter by making use of the encryptACharacter() method.
void setKey(int key) This method will set the value of the key data member. (You may NOT change the name of the input parameter)
1.4. Write a back-end class called AdvancedAPM11A1Encryptor and save it in a file called AdvancedAPM11A1Encryptor.cpp. This class must inherit the functionality of the APM11A1Encryptor class and add functionality that will enable us to make use of the ExclusiveOR encryption procedure. This class must have the following structure:
Inherited Data Members
Data
Type Name Description
int key This member will store the key that will be used during the encryption process.
Public Methods
Return
Type Method Signature Description
char encryptACharacter(char character) This method must encrypt the received character by using the key class member and the ExclusiveOR encryption technique.
Inherited Methods
Method Signature
encryptPage(Page page), setKey(int key)
1.5. Write a main program and save it in a file called Run.cpp. In this program you must read a text file that contains sentences into a Page object, encrypt the content using the APM11A1Encryptor class and then write the Page to a new text file called encrypt1.txt by using the PageManager class.
1.6.
Read the content of the same source text file into a second Page object, encrypt the content by making use of the AdvancedAPM11A1Encryptor class and then write the Page to a text file called encrypt2.txt by using the PageManager class.
During both encryption processes make use of the same key value.
After executing your Run.cpp file, open the newly created text files and compare their content. If your encryption worked, the content of the two files should differ.
NB: This Lab Ex must be submitted by 23:59, Tuesday 14th of March 2023