Vigenère Cipher - GeeksforGeeks (2024)

// C++ code to implement Vigenere Cipher#include <bits/stdc++.h>using namespace std;// This function generates the key in// a cyclic manner until it's length isn't// equal to the length of original textstring 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;}// This function returns the encrypted text// generated with the help of the keystring cipherText(string str, string key){ string cipher_text; for (int i = 0; i < str.size(); i++) { // converting in range 0-25 char x = (str[i] + key[i]) % 26; // convert into alphabets(ASCII) x += 'A'; cipher_text.push_back(x); } return cipher_text;}// This function decrypts the encrypted text// and returns the original textstring originalText(string cipher_text, string key){ string orig_text; for (int i = 0; i < cipher_text.size(); i++) { // converting in range 0-25 char x = (cipher_text[i] - key[i] + 26) % 26; // convert into alphabets(ASCII) x += 'A'; orig_text.push_back(x); } return orig_text;}// Driver program to test the above functionint main(){ string str = "GEEKSFORGEEKS"; string keyword = "AYUSH"; if (any_of(str.begin(), str.end(), ::islower)) transform(str.begin(), str.end(), str.begin(), ::toupper); if (any_of(keyword.begin(), keyword.end(), ::islower)) transform(keyword.begin(), keyword.end(), keyword.begin(), ::toupper); string key = generateKey(str, keyword); string cipher_text = cipherText(str, key); cout << "Ciphertext : " << cipher_text << "\n"; cout << "Original/Decrypted Text : " << originalText(cipher_text, key); return 0;}

// Java code to implement Vigenere Cipherclass GFG {// This function generates the key in// a cyclic manner until it's length isi'nt// equal to the length of original textstatic String generateKey(String str, String key){ int x = str.length(); for (int i = 0; ; i++) { if (x == i) i = 0; if (key.length() == str.length()) break; key+=(key.charAt(i)); } return key;}// This function returns the encrypted text// generated with the help of the keystatic String cipherText(String str, String key){ String cipher_text=""; for (int i = 0; i < str.length(); i++) { // converting in range 0-25 int x = (str.charAt(i) + key.charAt(i)) %26; // convert into alphabets(ASCII) x += 'A'; cipher_text+=(char)(x); } return cipher_text;}// This function decrypts the encrypted text// and returns the original textstatic String originalText(String cipher_text, String key){ String orig_text=""; for (int i = 0 ; i < cipher_text.length() &&  i < key.length(); i++) { // converting in range 0-25 int x = (cipher_text.charAt(i) -  key.charAt(i) + 26) %26; // convert into alphabets(ASCII) x += 'A'; orig_text+=(char)(x); } return orig_text;}// This function will convert the lower case character to Upper casestatic String LowerToUpper(String s){ StringBuffer str =new StringBuffer(s);  for(int i = 0; i < s.length(); i++) { if(Character.isLowerCase(s.charAt(i))) { str.setCharAt(i, Character.toUpperCase(s.charAt(i))); } } s = str.toString(); return s;}// Driver codepublic static void main(String[] args) { String Str = "GEEKSFORGEEKS"; String Keyword = "AYUSH";  String str = LowerToUpper(Str); String keyword = LowerToUpper(Keyword); String key = generateKey(str, keyword); String cipher_text = cipherText(str, key); System.out.println("Ciphertext : " + cipher_text + "\n"); System.out.println("Original/Decrypted Text : " + originalText(cipher_text, key)); }}// This code has been contributed by 29AjayKumar

def generate_key(msg, key): key = list(key) if len(msg) == len(key): return key else: for i in range(len(msg) - len(key)): key.append(key[i % len(key)]) return "".join(key)def encrypt_vigenere(msg, key): encrypted_text = [] key = generate_key(msg, key) for i in range(len(msg)): char = msg[i] if char.isupper(): encrypted_char = chr((ord(char) + ord(key[i]) - 2 * ord('A')) % 26 + ord('A')) elif char.islower(): encrypted_char = chr((ord(char) + ord(key[i]) - 2 * ord('a')) % 26 + ord('a')) else: encrypted_char = char encrypted_text.append(encrypted_char) return "".join(encrypted_text)def decrypt_vigenere(msg, key): decrypted_text = [] key = generate_key(msg, key) for i in range(len(msg)): char = msg[i] if char.isupper(): decrypted_char = chr((ord(char) - ord(key[i]) + 26) % 26 + ord('A')) elif char.islower(): decrypted_char = chr((ord(char) - ord(key[i]) + 26) % 26 + ord('a')) else: decrypted_char = char decrypted_text.append(decrypted_char) return "".join(decrypted_text)# Example usagetext_to_encrypt = "Hello, World!"key = "KEY"encrypted_text = encrypt_vigenere(text_to_encrypt, key)print(f"Encrypted Text: {encrypted_text}")decrypted_text = decrypt_vigenere(encrypted_text, key)print(f"Decrypted Text: {decrypted_text}")#previous code was only support the upper case letters#this code can be apply on both

// C# code to implement Vigenere Cipherusing System; class GFG {// This function generates the key in// a cyclic manner until it's length isi'nt// equal to the length of original textstatic String generateKey(String str, String key){ int x = str.Length; for (int i = 0; ; i++) { if (x == i) i = 0; if (key.Length == str.Length) break; key+=(key[i]); } return key;}// This function returns the encrypted text// generated with the help of the keystatic String cipherText(String str, String key){ String cipher_text=""; for (int i = 0; i < str.Length; i++) { // converting in range 0-25 int x = (str[i] + key[i]) %26; // convert into alphabets(ASCII) x += 'A'; cipher_text+=(char)(x); } return cipher_text;}// This function decrypts the encrypted text// and returns the original textstatic String originalText(String cipher_text, String key){ String orig_text=""; for (int i = 0 ; i < cipher_text.Length &&  i < key.Length; i++) { // converting in range 0-25 int x = (cipher_text[i] -  key[i] + 26) %26; // convert into alphabets(ASCII) x += 'A'; orig_text+=(char)(x); } return orig_text;}// Driver codepublic static void Main(String[] args) { String str = "GEEKSFORGEEKS"; String keyword = "AYUSH"; str = str.ToUpper(); keyword = keyword.ToUpper(); String key = generateKey(str, keyword); String cipher_text = cipherText(str, key); Console.WriteLine("Ciphertext : " + cipher_text + "\n"); Console.WriteLine("Original/Decrypted Text : " + originalText(cipher_text, key)); }}/* This code contributed by PrinciRaj1992 */

// JavaScript code to implement Vigenere Cipher// This function generates the key in// a cyclic manner until it's length isn't// equal to the length of original textfunction generateKey(str,key){  key=key.split(""); if(str.length == key.length) return key.join(""); else { let temp=key.length;  for (let i = 0;i<(str.length-temp) ; i++) {  key.push(key[i % ((key).length)]) } } return key.join("");}// This function returns the encrypted text// generated with the help of the keyfunction cipherText(str,key){ let cipher_text="";  for (let i = 0; i < str.length; i++) { // converting in range 0-25 let x = (str[i].charCodeAt(0) + key[i].charCodeAt(0)) %26;  // convert into alphabets(ASCII) x += 'A'.charCodeAt(0);  cipher_text+=String.fromCharCode(x); } return cipher_text;}// This function decrypts the encrypted text// and returns the original textfunction originalText(cipher_text,key){ let orig_text="";  for (let i = 0 ; i < cipher_text.length ; i++) { // converting in range 0-25 let x = (cipher_text[i].charCodeAt(0) - key[i].charCodeAt(0) + 26) %26;  // convert into alphabets(ASCII) x += 'A'.charCodeAt(0); orig_text+=String.fromCharCode(x); } return orig_text;}// This function will convert the lower// case character to Upper casefunction LowerToUpper(s){ let str =(s).split(""); for(let i = 0; i < s.length; i++) { if(s[i] == s[i].toLowerCase()) { str[i] = s[i].toUpperCase(); } } s = str.toString(); return s;}// Driver codelet str = "GEEKSFORGEEKS";let keyword = "AYUSH";str = str.toUpperCase();keyword = keyword.toUpperCase();let key = generateKey(str, keyword);let cipher_text = cipherText(str, key);console.log("Ciphertext : " + cipher_text + "<br><br>");console.log("Original/Decrypted Text : " + originalText(cipher_text, key)+"<br>");