From 560011163f1f611aa44bd73736f31d973aa4f527 Mon Sep 17 00:00:00 2001
From: Pranav Sharma <pranav761@gmail.com>
Date: Fri, 9 Oct 2020 17:46:12 +0530
Subject: [PATCH] Create Vigener_cipher.cpp

---
 Vigener_cipher.cpp | 80 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 Vigener_cipher.cpp

diff --git a/Vigener_cipher.cpp b/Vigener_cipher.cpp
new file mode 100644
index 0000000..0a6bb99
--- /dev/null
+++ b/Vigener_cipher.cpp
@@ -0,0 +1,80 @@
+#include<bits/stdc++.h> 
+using namespace std; 
+
+string generateKey(string str, string key) 
+{ 
+	int x = str.size();
+	for (int i = 0; ; i++)
+	{
+		if (x == i) 
+			i = 0; 
+		if (key.size() == str.size()) 
+			break; 
+		key.push_back(key[i]); 
+	} 
+	return key; 
+} 
+
+string encrypt(string str, string key) 
+{ 
+	string cipher_text; 
+
+	for (int i = 0; i < str.size(); i++) 
+	{ 
+		char x = (((str[i] + key[i]) %26) + 65);
+		cipher_text.push_back(x); 
+	} 
+	return cipher_text; 
+} 
+
+string decrypt(string cipher_text, string key) 
+{ 
+	string orig_text; 
+
+	for (int i = 0 ; i < cipher_text.size(); i++) 
+	{ 
+		char x = (((cipher_text[i] - key[i] + 26) %26) +65); 
+		orig_text.push_back(x); 
+	} 
+	return orig_text; 
+} 
+
+int main() 
+{ 
+
+    string text="", keyword="", key=""; 
+    int sel=0;
+    char ch='y'; 
+	cout<<"===VIGENERE CIPHER==="<<endl;
+	
+	do {
+		cout<<"\nMenu\n1.Encrypt\n2.Decrypt\n";
+		cout << "Enter the input : ";
+		cin>>sel;
+		switch(sel) {
+			case 1:
+				cout << "Enter the text : ";
+				cin.ignore();
+				getline(cin,text); 	
+				cout<< "Enter the key: ";
+				getline(cin,keyword);
+				key = generateKey(text,keyword);
+				cout << "Encrypted Text is(Cipher Text) : " << encrypt(text,key) <<endl;
+				break;
+			case 2:
+				cout << "Enter the text : ";
+				cin.ignore();
+				getline(cin,text);
+				cout<<"Using the key provided earlier"<<endl;
+				key = generateKey(text,keyword);
+				cout << "Decrypted Text is(Plain Text) : " << decrypt(text, key) <<endl;
+				break;
+			default:
+				cout<<"Enter the correct option";
+				break;
+			}
+			cout<<"If you wish to exit press n else press any key: ";
+			cin>>ch;
+		}while(ch!='n');
+	return 0;
+}