php-使用php开发的cipher加密算法之VignereCipher-加密算法实现.zip

<?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; }