From 4e442a465e564d0449b82f4bfb8088f1e6622978 Mon Sep 17 00:00:00 2001
From: Ajay Reddy Chinthala <ajayreddychinthala110125@gmail.com>
Date: Tue, 28 Mar 2023 21:35:34 +0530
Subject: [PATCH] ROT13 Cipher

ROT13 Cipher Implementation in php
---
 Ciphers/ROT13_Cipher.php | 53 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 Ciphers/ROT13_Cipher.php

diff --git a/Ciphers/ROT13_Cipher.php b/Ciphers/ROT13_Cipher.php
new file mode 100644
index 00000000..f72d2554
--- /dev/null
+++ b/Ciphers/ROT13_Cipher.php
@@ -0,0 +1,53 @@
+<?php
+
+/**
+ * Encrypt given text using ROT 13 cipher.
+ *
+ * @param string text text to be encrypted
+ * @return string new encrypted text
+ */
+    function encrypt(string $text): string
+    {
+        $encryptedText = ''; // Empty string to store encrypted text
+        foreach (str_split($text) as $c) { // Going through each character
+            if (ctype_alpha($c)) {
+                $placeValue = ord($c) - ord(ctype_upper($c) ? 'A' : 'a'); // Getting value of character (i.e. 0-25)
+                $placeValue = ($placeValue + 13) % 26; // Applying encryption formula
+                $placeValue += ord(ctype_upper($c) ? 'A' : 'a');
+                $newChar = chr($placeValue); // Getting new character from new value (i.e. A-Z)
+                $encryptedText .= $newChar; // Appending encrypted character
+            } else {
+                $encryptedText .= $c; // Appending the original character
+            }
+        }
+
+        return $encryptedText; // Returning encrypted text
+    }
+/**
+ * Decrypt given text using ROT 13 cipher.
+ *
+ * @param string text text to be Decrypted
+
+ * @return string new Decrypted text
+ */
+    function decrypt(string $text): string
+    {
+        $decryptedText = ''; // Empty string to store decrypted text
+        foreach (str_split($text) as $c) { // Going through each character
+            if (ctype_alpha($c)) {
+                $placeValue = ord($c) - ord(ctype_upper($c) ? 'A' : 'a'); // Getting value of character (i.e. 0-25)
+                $placeValue = ($placeValue - 13) % 26; // Applying decryption formula
+                if ($placeValue < 0) { // Handling case where remainder is negative
+                    $placeValue += 26;
+                }
+                $placeValue += ord(ctype_upper($c) ? 'A' : 'a');
+                $newChar = chr($placeValue); // Getting new character from new value (i.e. A-Z)
+                $decryptedText .= $newChar; // Appending decrypted character
+            } else {
+                $decryptedText .= $c; // Appending the original character
+            }
+        }
+
+        return $decryptedText; // Returning decrypted text
+    }
+?>
\ No newline at end of file