AES-256 encryption and decryption in PHP and C#
PHP
<?php $plaintext = 'My secret message 1234'; $password = '3sc3RLrpd17'; // CBC has an IV and thus needs randomness every time a message is encrypted $method = 'aes-256-cbc'; // Must be exact 32 chars (256 bit) // You must store this secret random key in a safe place of your system. $key = substr(hash('sha256', $password, true), 0, 32); echo "Password:" . $password . "\n"; // Most secure key //$key = openssl_random_pseudo_bytes(openssl_cipher_iv_length($method)); // IV must be exact 16 chars (128 bit) $iv = chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0) . chr(0x0); // Most secure iv // Never ever use iv=0 in real life. Better use this iv: // $ivlen = openssl_cipher_iv_length($method); // $iv = openssl_random_pseudo_bytes($ivlen); // av3DYGLkwBsErphcyYp+imUW4QKs19hUnFyyYcXwURU= $encrypted = base64_encode(openssl_encrypt($plaintext, $method, $key, OPENSSL_RAW_DATA, $iv)); // My secret message 1234 $decrypted = openssl_decrypt(base64_decode($encrypted), $method, $key, OPENSSL_RAW_DATA, $iv); echo 'plaintext=' . $plaintext . "\n"; echo 'cipher=' . $method . "\n"; echo 'encrypted to: ' . $encrypted . "\n"; echo 'decrypted to: ' . $decrypted . "\n\n";
C#
using System.Security.Cryptography; using System.IO; using System.Text; using System; public string EncryptString(string plainText, byte[] key, byte[] iv) { // Instantiate a new Aes object to perform string symmetric encryption Aes encryptor = Aes.Create(); encryptor.Mode = CipherMode.CBC; // Set key and IV byte[] aesKey = new byte[32]; Array.Copy(key, 0, aesKey, 0, 32); encryptor.Key = aesKey; encryptor.IV = iv; // Instantiate a new MemoryStream object to contain the encrypted bytes MemoryStream memoryStream = new MemoryStream(); // Instantiate a new encryptor from our Aes object ICryptoTransform aesEncryptor = encryptor.CreateEncryptor(); // Instantiate a new CryptoStream object to process the data and write it to the // memory stream CryptoStream cryptoStream = new CryptoStream(memoryStream, aesEncryptor, CryptoStreamMode.Write); // Convert the plainText string into a byte array byte[] plainBytes = Encoding.ASCII.GetBytes(plainText); // Encrypt the input plaintext string cryptoStream.Write(plainBytes, 0, plainBytes.Length); // Complete the encryption process cryptoStream.FlushFinalBlock(); // Convert the encrypted data from a MemoryStream to a byte array byte[] cipherBytes = memoryStream.ToArray(); // Close both the MemoryStream and the CryptoStream memoryStream.Close(); cryptoStream.Close(); // Convert the encrypted byte array to a base64 encoded string string cipherText = Convert.ToBase64String(cipherBytes, 0, cipherBytes.Length); // Return the encrypted data as a string return cipherText; } public string DecryptString(string cipherText, byte[] key, byte[] iv) { // Instantiate a new Aes object to perform string symmetric encryption Aes encryptor = Aes.Create(); encryptor.Mode = CipherMode.CBC; // Set key and IV byte[] aesKey = new byte[32]; Array.Copy(key, 0, aesKey, 0, 32); encryptor.Key = aesKey; encryptor.IV = iv; // Instantiate a new MemoryStream object to contain the encrypted bytes MemoryStream memoryStream = new MemoryStream(); // Instantiate a new encryptor from our Aes object ICryptoTransform aesDecryptor = encryptor.CreateDecryptor(); // Instantiate a new CryptoStream object to process the data and write it to the // memory stream CryptoStream cryptoStream = new CryptoStream(memoryStream, aesDecryptor, CryptoStreamMode.Write); // Will contain decrypted plaintext string plainText = String.Empty; try { // Convert the ciphertext string into a byte array byte[] cipherBytes = Convert.FromBase64String(cipherText); // Decrypt the input ciphertext string cryptoStream.Write(cipherBytes, 0, cipherBytes . Length); // Complete the decryption process cryptoStream.FlushFinalBlock(); // Convert the decrypted data from a MemoryStream to a byte array byte[] plainBytes = memoryStream.ToArray(); // Convert the decrypted byte array to string plainText = Encoding.ASCII.GetString(plainBytes, 0, plainBytes.Length); } finally { // Close both the MemoryStream and the CryptoStream memoryStream.Close(); cryptoStream.Close(); } // Return the decrypted data as a string return plainText; }
Usage
string message = "My secret message 1234"; string password = "3sc3RLrpd17"; // Create sha256 hash SHA256 mySHA256 = SHA256Managed.Create(); byte[] key = mySHA256.ComputeHash(Encoding.ASCII.GetBytes(password)); // Create secret IV byte[] iv = new byte[16] { 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 }; string encrypted = this.EncryptString(message, key, iv); string decrypted = this.DecryptString(encrypted, key, iv); Console.WriteLine(encrypted); Console.WriteLine(decrypted);
FROM https://odan.github.io/2017/08/10/aes-256-encryption-and-decryption-in-php-and-csharp.html