using System.Security.Cryptography;
using System.Text;

static string Encrypt(string plainText, byte[] secretKey) {
	using Aes aes = Aes.Create();
	aes.Key = secretKey;

	// Convert the plain text string into a byte array
	byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

	// Create an encryptor using the AES service and its initialization vector (IV)
	ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);

	// Perform the encryption
	byte[] encrypted = encryptor.TransformFinalBlock(plainTextBytes, 0, plainTextBytes.Length);

	// Create a new byte array to hold the IV and the encrypted data
	byte[] result = new byte[aes.IV.Length + encrypted.Length];

	// Copy the IV and encrypted data into the result byte array
	Buffer.BlockCopy(aes.IV,    0, result, 0,             aes.IV.Length);
	Buffer.BlockCopy(encrypted, 0, result, aes.IV.Length, encrypted.Length);

	return Convert.ToBase64String(result);
}

static string Decrypt(string encryptedText, byte[] secretKey) {
	using Aes aes = Aes.Create();
	aes.Key = secretKey;

	// Decode the base64 string into a byte array
	byte[] fullCipher = Convert.FromBase64String(encryptedText);

	// Create byte arrays to hold the IV and the encrypted data
	byte[] iv = new byte[aes.BlockSize / 8];
	byte[] cipher = new byte[fullCipher.Length - iv.Length];

	// Copy the IV and encrypted data from the full cipher byte array
	Buffer.BlockCopy(fullCipher, 0, iv, 0, iv.Length);
	Buffer.BlockCopy(fullCipher, iv.Length, cipher, 0, cipher.Length);

	// Assign the IV to the AES service
	aes.IV = iv;

	// Create a decryptor using the AES service
	ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);

	// Perform the decryption
	byte[] decrypted = decryptor.TransformFinalBlock(cipher, 0, cipher.Length);

	// Convert the decrypted byte array back into a string
	return Encoding.UTF8.GetString(decrypted);
}


Console.WriteLine("Hello, World!");

string key = "REDACTED_BASE64_STRING";
byte[] secretKey = Convert.FromBase64String(key);

try {
	string input = "Hello, world!";
	Console.WriteLine("Original text: " + input);

	string encryptedText = Encrypt(input, secretKey);
	Console.WriteLine("Encrypted text: " + encryptedText);

	string decrypted = Decrypt(encryptedText, secretKey);
	Console.WriteLine("Decrypted text: " + decrypted);
} catch (Exception e) {
	Console.WriteLine(e);
}