From 4a4b18ed045e8eb6821e427200a8d87daad59685 Mon Sep 17 00:00:00 2001
From: Tharakadhanushka <55351120+Tharakadhanushka@users.noreply.github.com>
Date: Sun, 15 Oct 2023 10:07:25 +0530
Subject: [PATCH] Create SubstitutionCipher.js

SubstitutionCipher
---
 Ciphers/SubstitutionCipher.js | 45 +++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 Ciphers/SubstitutionCipher.js

diff --git a/Ciphers/SubstitutionCipher.js b/Ciphers/SubstitutionCipher.js
new file mode 100644
index 0000000000..b98ac8cb51
--- /dev/null
+++ b/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);