Create SubstitutionCipher.js

Ciphers/SubstitutionCipher.js

@@ -0,0 +1,45 @@
+function createCipher(key) {
+ const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
+ const cipher = {};
+
+ for (let i = 0; i < alphabet.length; i++) {
+ cipher[alphabet[i]] = key[i] || alphabet[i];
+ }
+
+ return cipher;
+}
+
+function encrypt(plainText, cipher) {
+ return plainText
+ .toUpperCase() // Convert to uppercase for consistency
+ .split('')
+ .map(char => cipher[char] || char)
+ .join('');
+}
+
+function decrypt(encryptedText, cipher) {
+ const reverseCipher = {};
+ for (const key in cipher) {
+ if (cipher.hasOwnProperty(key)) {
+ reverseCipher[cipher[key]] = key;
+ }
+ }
+
+ return encryptedText
+ .toUpperCase()
+ .split('')
+ .map(char => reverseCipher[char] || char)
+ .join('');
+}
+
+// Example usage:
+const key = 'XZVTPONMLKJIHGFEDCBA';
+const text = 'Hello, World!';
+
+const cipher = createCipher(key);
+const encryptedText = encrypt(text, cipher);
+const decryptedText = decrypt(encryptedText, cipher);
+
+console.log('Original text:', text);
+console.log('Encrypted text:', encryptedText);
+console.log('Decrypted text:', decryptedText);