using System;

using System.IO;

using System.Text;

using System.Security.Cryptography;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        //Aes aes = Aes.Create();

        string plainText = "Hello world!!";

        string key = "rfh06LQNQmIAp0CKJHfEftuhBVNUw2we";

        string iv = "rfh06LQNQmIAp0CK";

        Console.WriteLine("key = " + key + ", length = " + key.Length);

        Console.WriteLine("iv = " + iv + ", length = " + iv.Length);

        key = GenerateNewAESKey(32);

        iv = GetIVFromKey(key);

        Console.WriteLine("plainText = " + plainText);

        Console.WriteLine("key = " + key + ", length = " + key.Length);

        Console.WriteLine("iv = " + iv + ", length = " + iv.Length);

        byte[] keyBytes = Encoding.ASCII.GetBytes(key);

        byte[] ivBytes = Encoding.ASCII.GetBytes(iv);

        Console.WriteLine("keyBytes length = " + keyBytes.Length);

        Console.WriteLine("ivBytes length = " + ivBytes.Length);

        byte[] encryptedBytes = EncryptStringToBytesAES(plainText, keyBytes, ivBytes);

        string encryptedBase64 = Convert.ToBase64String(encryptedBytes);

        Console.WriteLine("encryptedBytes = " + JsonConvert.SerializeObject(encryptedBytes));

        Console.WriteLine("encryptedBase64 = " + encryptedBase64);

        byte[] encryptedBytes2 = Convert.FromBase64String(encryptedBase64);

        string decryptedText = DecryptStringFromBytesAES(encryptedBytes2, keyBytes, ivBytes);

        Console.WriteLine("encryptedBytes2 = " + JsonConvert.SerializeObject(encryptedBytes2));

        Console.WriteLine("decryptedText = " + decryptedText);

    }

    internal static readonly char[] chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".ToCharArray();

    public static string GenerateNewAESKey(int length)

    {

        byte[] data = new byte[4*length];

        using (RNGCryptoServiceProvider crypto = new RNGCryptoServiceProvider())

        {

            crypto.GetBytes(data);

        }

        StringBuilder result = new StringBuilder(length);

        for (int i = 0; i < length; i++)

        {

            var rnd = BitConverter.ToUInt32(data, i * 4);

            var idx = rnd % chars.Length;

            result.Append(chars[idx]);

        }

        return result.ToString();

    }

    public static string GetIVFromKey(string key)

    {

        return key.Substring(0, 16);

    }

    public static byte[] EncryptStringToBytesAES(string plainText, byte[] key, byte[] iv)

    {

        if (plainText == null || plainText.Length <= 0)

            throw new ArgumentNullException("plainText");

        if (key == null || key.Length != 32)

            throw new ArgumentNullException("key");

        if (iv == null || iv.Length <= 0)

            throw new ArgumentNullException("iv");

        byte[] encrypted;

        // Create an Aes object

        // with the specified key and IV.

        using (Aes aesAlg = Aes.Create())

        {

            aesAlg.Mode = CipherMode.CBC;

            aesAlg.Padding = PaddingMode.PKCS7;

            aesAlg.KeySize = 256;

            aesAlg.BlockSize = 128;

            //aesAlg.Key = key;

            //aesAlg.IV = iv;

​

            // Create an encryptor to perform the stream transform.

            ICryptoTransform encryptor = aesAlg.CreateEncryptor(key, iv);

            // Create the streams used for encryption.

            using (MemoryStream msEncrypt = new MemoryStream())

            {

                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))

                {

                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))

                    {

                        //Write all data to the stream.

                        swEncrypt.Write(plainText);

                    }

                    encrypted = msEncrypt.ToArray();

                }

            }

        }

        // Return the encrypted bytes from the memory stream.

        return encrypted;

    }

    public static string DecryptStringFromBytesAES(byte[] cipherText, byte[] key, byte[] iv)

    {

        // Check arguments.

        if (cipherText == null || cipherText.Length <= 0)

            throw new ArgumentNullException("cipherText");

        if (key == null || key.Length != 32)

            throw new ArgumentNullException("key");

        if (iv == null || iv.Length <= 0)

            throw new ArgumentNullException("iv");

        // Declare the string used to hold

        // the decrypted text.

        string plaintext = null;

        // Create an Aes object

        // with the specified key and IV.

        using (Aes aesAlg = Aes.Create())

        {

            aesAlg.Mode = CipherMode.CBC;

            aesAlg.Padding = PaddingMode.PKCS7;

            aesAlg.KeySize = 256;

            aesAlg.BlockSize = 128;

            //aesAlg.Key = key;

            //aesAlg.IV = iv;

            // Create a decryptor to perform the stream transform.

            ICryptoTransform decryptor = aesAlg.CreateDecryptor(key, iv);

            // Create the streams used for decryption.

            using (MemoryStream msDecrypt = new MemoryStream(cipherText))

            {

                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))

                {

                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))

                    {

                        // Read the decrypted bytes from the decrypting stream

                        // and place them in a string.

                        plaintext = srDecrypt.ReadToEnd();

                    }

                }

            }

        }

        return plaintext;

    }

}