vigenere_square.cpp

This program encodes and decodes a character using the Vigenere Square method

// Solution: Vigenere Square
// File: vigenere_square.cpp
// Programmed by: Jay Catelli
// EMail: [e-mail]
// Date: 3/11/04
//
// Discription: This program encodes and decodes a character using
//              the Vigenere Square method
//
// Compiler: Microsoft Visual C++ .Net
// Build: 54 final
// Build Date: 3/12/04 3:01:32 AM

// include libaries
#include <iostream>

// Namespaces
using namespace std;

// Globle Constant Varables
const int size=26;	// The maxium size of the matrix

void create_vigenere_square(char matrix[][size])
// This function creates a Vigenere Square
// Pre: This funtion takes in a matrix size by size
// Post: This funtion returns (passes back) the Vigenere Square to matrix
{
	for (int i=0;i<size;i++)
		for (int j=0;j<size;j++)
			matrix[i][j]=char(((i+j)%size)+'A');
}

char encode_from_square(char key, char plainchar,const char matrix[][size])
// This function takes plainchar and encodes it with the key using
// the Vigenere Square
// Pre: This function takes in a key char, a plainchar char, and the
//      matrix holding the Vigenere Square. Note: All chars are upper case
// Post: This funtion returns the cipherchar char for the plainchar
//       using the key
{
	// Declaring Vars
	char cipherchar; // Var to hold the cipher char
	int row; // Var to hold the row number which is based off the plainchar
	int col; // Var to hold the col number which is based off the key

	// Finding the cipher char
	row=int(plainchar-'A');
	col=int(key-'A');
	cipherchar=matrix[row][col];

	// Return the cipherchar
	return (cipherchar);
}

char decode_from_square(char key, char cipherchar,const char matrix[][size])
// This function takes chpherchar and decodes it with the key using
// the Vigenere Square
// Pre: This function takes in a key char, a cipherchar char, and the
//      matrix holding the Vigenere Square. Note: All chars are upper case
// Post: This function returns the plainchar for the cipherchar using
//       the key
{
	// Declaring Vars
	char plainchar; // Var to hold the plain char
	int row; // Var to hold the row number which is found in the Square
	int col; // Var to hold the col number which is based off the key

	// Finding the plain char
	row=0;
	col=int(key-'A');
	while (matrix[row][col]!=cipherchar)
		row++;
	plainchar=char(row+'A');

	// Return the row that holds the cipherchar in char form
	return (plainchar);
}

void encode_menu(const char matrix[][size])
// This function diplays the encode menu
// Pre:
// Post: Runs the encode_from_square_function
{
	// Declare Vars
	char key;
	char plainchar;
	char cipherchar;

	// Get the key
	do
	{
		cout<<"Please enter in your key : ";cin>>key;
		// Check entery
		if (islower(key))
			key-='a'-'A';
		else if (!isupper(key))
			cout<<endl<<key<<" is not a vaild key."<<endl<<endl;
	} while (!isupper(key));
	// Get the plainchar
	cout<<endl;
	do
	{
		cout<<"Please enter your plainchar : ";cin>>plainchar;
		// Check entery
		if (islower(plainchar))
			plainchar-='a'-'A';
		else if (!isupper(plainchar))
			cout<<endl<<plainchar<<" is not a vaild plainchar."<<endl<<endl;
	} while (!isupper(plainchar));
	// Encode the plainchar
	cout<<endl;
	cipherchar=encode_from_square(key, plainchar, matrix);
	// Display result
	cout<<"Your encoded char for "<<plainchar<<" using "<<key<<" as the key"
		<<" is : "<<cipherchar<<endl;
	cout<<endl;
	cout<<"Please press enter to continue.";cin.ignore();getchar();
}

void decode_menu(const char matrix[][size])
// This function diplays the decode menu
// Pre:
// Post: Runs the decode_from_square_function
{
	// Declare Vars
	char key;
	char plainchar;
	char cipherchar;

	// Get the key
	do
	{
		cout<<"Please enter in your key : ";cin>>key;
		// Check entery
		if (islower(key))
			key-='a'-'A';
		else if (!isupper(key))
			cout<<endl<<key<<" is not a vaild key."<<endl<<endl;
	} while (!isupper(key));
	// Get the cipherchar
	cout<<endl;
	do
	{
		cout<<"Please enter your cipherchar : ";cin>>cipherchar;
		// Check entery
		if (islower(cipherchar))
			cipherchar-='a'-'A';
		else if (!isupper(cipherchar))
			cout<<endl<<cipherchar<<" is not a vaild cipherchar."<<endl<<endl;
	} while (!isupper(cipherchar));
	// Encode the cipherchar
	cout<<endl;
	plainchar=decode_from_square(key, cipherchar, matrix);
	// Display result
	cout<<"Your decoded char for "<<cipherchar<<" using "<<key<<" as the key"
		<<" is : "<<plainchar<<endl;
	cout<<endl;
	cout<<"Please press enter to continue.";cin.ignore();getchar();
}

void print_square(const char matrix[][size])
// This function print out the Vigenere Square
// Pre: Takes in the matrix which holds the Vigenere Square
// Post: Displays the Vigenere Square
{
	// Print the key guide
	cout<<"  ";
	for (char i='A';i<='Z';i++)
		cout<<'|'<<i;
	cout<<endl;
	for (int i=0;i<53;i++)
		cout<<'-';
	cout<<endl;
	// Print out the plainchar guide with the row in the matrix
	for (char i='A';i<='Z';i++)
	{
		cout<<i<<"| ";
		for (int j=0;j<size;j++)
			cout<<matrix[int(i-'A')][j]<<' ';
		cout<<endl;
	}
	cout<<"Please press enter to continue.";cin.ignore();getchar();
}

void menu(const char matrix[][size])
// This function displays the program menu
// Pre:
// Post: This function calls encode and decode until the user quits
{
	// Declare Vars
	char choice='E'; // Var to hold the choice of the menu

	// Display Menu
	do
	{
		system("cls");
		if (!(choice=='E'||choice=='D'||choice=='P'))
			cout<<"Invaild Choice.   Please try again."<<endl<<endl;
		cout<<"Welcome to Vigenere Square Cipher Program"<<endl;
		cout<<endl;
		cout<<"E : Encode a character"<<endl;
		cout<<"D : Decode a character"<<endl;
		cout<<"P : Print the Vigenere Square"<<endl;
		cout<<"Q : To quit"<<endl;
		cout<<endl;
		cout<<"Please enter in your choice: ";cin>>choice;
		// Check and see if input is in range if not make it so
		if (islower(choice))
			choice-='a'-'A';
		system("cls");
		// Preform require fuctions for choice
		switch (choice)
		{
			case 'E':
				encode_menu(matrix);
				break;
			case 'D':
				decode_menu(matrix);
				break;
			case 'P':
				print_square(matrix);
				break;
			default:
				break;
		}
	} while (choice!='Q');
}

int main()
{
	char matrix[size][size]; // Matrix to hold the Vigener Square

	// Make the Vigenere Square
	create_vigenere_square(matrix);
	// Display the Program Menu
	menu(matrix);

	return (0);
}