decryption

#include <iostream>
#include <string>
using namespace std;

string encryptCaesar(string plaintext, int rshift); //creates a string that will be utilized to encrypt words into Caesar
string encryptVigenere(string plaintext, string keyword); //creates a string that will encrypt words into Vigenere

string decryptCaesar(string ciphertext, int rshift); //creates a string that will be utilized to decrypt words into Caesar
string decryptVigenere(string ciphertext, string keyword); //creates a string that will decrypt words into Vigenere

string encryptCaesar(string plaintext, int rshift){
 char c; //creates character from variable c

for (int i = 0; plaintext[i] != '\0'; i++){ //use for statement to create string variable with integer i for encryption
  c = plaintext[i];

if (c >= 'a' && c <= 'z'){ //shifts character in relation to what letters are used
  c = c + rshift;
if (c > 'z'){
 c = c - 'z' + 'a' - 1;
}
plaintext[i] = c;
}
else if (c >= 'A' && c <= 'Z'){ 
c = c + rshift;
if (c > 'Z'){
 c = c - 'Z' + 'A' - 1;
}
 plaintext[i] = c;
 }
}
 return plaintext; //after processing the characters in relation to how it is encrypted, return the function
}

string decryptCaesar(string ciphertext, int rshift){
char c;

for (int i = 0; ciphertext[i] != '\0'; i++){ //use prior established integers and characters to decrypt the previously encrypted statement
    c = ciphertext[i];
if (c >= 'a' && c <= 'z'){
     c = c - rshift;
if (c < 'a'){
c = c + 'z' - 'a' + 1;
 }
ciphertext[i] = c;
}
else if (c >= 'A' && c <= 'Z'){
 c = c - rshift;
if (c < 'A'){ 
c = c + 'Z' - 'A' + 1;
}
ciphertext[i] = c;
 }
}
 return ciphertext; //returns the decrypted text based upon Caesar decryption
}

string encryptVigenere(string plaintext, string keyword) //creates a string that will encrypt words into Vigenere
{
string endResult = "";

char character;
int i = 0;
int encryptionKey;

for(int k = 0; k < plaintext.length(); k++)  //use for statement to create string variable with integer i for encryption
{
character = plaintext[k];

if(character >= 'A' && character <= 'Z')  //shifts character in relation to what letters are used
{
encryptionKey = keyword[i] - 'a';
i = (i + 1) % keyword.length();
character = 'A' + (character - 'A' + encryptionKey + 26) %26;
}
if(character >= 'a' && character <= 'z')
{
encryptionKey = keyword[i] - 'a';
i = (i + 1) % keyword.length();
character = 'a' + (character - 'a' + encryptionKey + 26) %26;
}
endResult += character;
}
return endResult; //after processing the characters in relation to how it is encrypted, return the function

}

string decryptVigenere(string ciphertext, string keyword)
{
string endResult = "";

char character;
int i = 0;
int decryptionKey;

for(int k = 0; k < ciphertext.length(); k++) //use prior established integers and characters to decrypt the previously encrypted statement
{
character = ciphertext[k];

if(character >= 'A' && character <= 'Z')
{
decryptionKey = keyword[i] - 'a';
i = (i + 1) % keyword.length();
character = 'A' + (character - 'A' - decryptionKey + 26) %26;
}
if(character >= 'a' && character <= 'z')
{
decryptionKey = keyword[i] - 'a';
i = (i + 1) % keyword.length();
character = 'a' + (character - 'a' - decryptionKey + 26) %26;
}
endResult += character;
}
return endResult; //returns the decrypted text based upon Vigenere decryption

}

int main(){
       
       string plaintext; //creates string for plaintext which will be the user input
       string keyword; //creates string for keyword which will be the user input

       int rshift;

       cout << "Enter plaintext: ";
       getline(cin, plaintext); //takes in user input while reading it

       cout << "\n= Caesar =\n";

       cout << "Enter shift: ";
       cin >> rshift; //takes in user input for how the plaintext will be shifted for encryption

       string cipher = encryptCaesar(plaintext, rshift);
       cout << "Ciphertext: " << cipher << "\n"; //outputs the encrypted Caesar text

       plaintext = decryptCaesar(cipher, rshift);
       cout << "Decrypted: " << plaintext << endl; //outputs the decrypted text

       cout << "\n= Vigenere =\n";
       cout << "Enter keyword: ";
       cin >> keyword;//takes in user input for keyword to encrypt Vigenere text

       string cipher_text = encryptVigenere(plaintext, keyword);
       cout << "Ciphertext: " << cipher_text << "\n";//outputs the encrypted Vigenere text
       cout << "Decrypted: " << decryptVigenere(cipher_text, keyword) << endl;//outputs the decrypted text

       return 0; //after outputting the encrypted Caesar and Vigenere texts, as well as the decrypted text, the program will end.

}