Added Vignere Cipher

Ciphers/VignereCipher.php

@@ -0,0 +1,63 @@
+<?php
+
+/**
+ * Encrypts a plaintext using the Vigenère cipher.
+ * (https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher)
+ *
+ * @param string $plaintext The plaintext to be encrypted.
+ * @param string $key The encryption key.
+ * @return string The encrypted text.
+ */
+function vigenere_encrypt($plaintext, $key): string
+{
+    // Convert the input to uppercase for consistency
+    $plaintext = strtoupper($plaintext);
+    $key = strtoupper($key);
+    $keyLength = strlen($key);
+    $encryptedText = "";
+    for ($i = 0; $i < strlen($plaintext); $i++) {
+        $char = $plaintext[$i];
+        if (ctype_alpha($char)) {
+            // Calculate the shift based on the key
+            $shift = ord($key[$i % $keyLength]) - ord('A');
+            // Apply the Vigenère encryption formula
+            $encryptedChar = chr(((ord($char) - ord('A') + $shift) % 26) + ord('A'));
+            // Append the encrypted character to the result
+            $encryptedText .= $encryptedChar;
+        } else {
+            // If the character is not alphabetic, leave it unchanged
+            $encryptedText .= $char;
+        }
+    }
+    return $encryptedText;
+}
+
+/**
+ * Decrypts a ciphertext using the Vigenère cipher.
+ *
+ * @param string $ciphertext The ciphertext to be decrypted.
+ * @param string $key The decryption key.
+ * @return string The decrypted text.
+ */
+function vigenere_decrypt($ciphertext, $key): string
+{
+    $ciphertext = strtoupper($ciphertext);
+    $key = strtoupper($key);
+    $keyLength = strlen($key);
+    $decryptedText = "";
+    for ($i = 0; $i < strlen($ciphertext); $i++) {
+        $char = $ciphertext[$i];
+        if (ctype_alpha($char)) {
+            // Calculate the shift based on the key
+            $shift = ord($key[$i % $keyLength]) - ord('A');
+            // Apply the Vigenère decryption formula
+            $decryptedChar = chr(((ord($char) - ord('A') - $shift + 26) % 26) + ord('A'));
+            // Append the decrypted character to the result
+            $decryptedText .= $decryptedChar;
+        } else {
+            // If the character is not alphabetic, leave it unchanged
+            $decryptedText .= $char;
+        }
+    }
+    return $decryptedText;
+}

DIRECTORY.md

@@ -4,6 +4,7 @@
   * [Caesarcipher](./Ciphers/CaesarCipher.php)
   * [Monoalphabeticcipher](./Ciphers/MonoAlphabeticCipher.php)
   * [Morsecode](./Ciphers/MorseCode.php)
+  * [Vignerecipher](./Ciphers/VignereCipher.php)
   * [Xorcipher](./Ciphers/XORCipher.php)
 
 ## Conversions
@@ -89,6 +90,7 @@
     * [Cipherstest](./tests/Ciphers/CiphersTest.php)
     * [Monoalphabeticciphertest](./tests/Ciphers/MonoAlphabeticCipherTest.php)
     * [Morsecodetest](./tests/Ciphers/MorseCodeTest.php)
+    * [Vignereciphertest](./tests/Ciphers/VignereCipherTest.php)
   * Conversions
     * [Conversionstest](./tests/Conversions/ConversionsTest.php)
   * Datastructures

tests/Ciphers/VignereCipherTest.php

@@ -0,0 +1,19 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+require_once __DIR__ . '/../../Ciphers/VignereCipher.php';
+
+class VignereCipher extends TestCase
+{
+    public function testVignereCipher()
+    {
+        $plaintext = "HELLO";
+        $key = "KEY";
+        $encryptedText = vigenere_encrypt($plaintext, $key);
+        $decryptedText = vigenere_decrypt($encryptedText, $key);
+
+        $this->assertEquals($plaintext, $decryptedText);
+    }
+}