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

public static class NetworkValideAesSdk
{
    static byte[] Sha256(string text) => SHA256.Create().ComputeHash(Encoding.UTF8.GetBytes(text));

    public static string EncryptData(string rawData, string aesKey)
    {
        using (var aes = Aes.Create())
        {
            aes.Key = Sha256(aesKey);
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.PKCS7;
            aes.GenerateIV();
            using (var enc = aes.CreateEncryptor())
            {
                var plain = Encoding.UTF8.GetBytes(rawData);
                var cipher = enc.TransformFinalBlock(plain, 0, plain.Length);
                var all = new byte[aes.IV.Length + cipher.Length];
                Buffer.BlockCopy(aes.IV, 0, all, 0, aes.IV.Length);
                Buffer.BlockCopy(cipher, 0, all, aes.IV.Length, cipher.Length);
                return Convert.ToBase64String(all);
            }
        }
    }

    public static string DecryptMsg(string msg, string aesKey)
    {
        var all = Convert.FromBase64String(msg);
        var iv = new byte[16];
        var cipher = new byte[all.Length - 16];
        Buffer.BlockCopy(all, 0, iv, 0, 16);
        Buffer.BlockCopy(all, 16, cipher, 0, cipher.Length);
        using (var aes = Aes.Create())
        {
            aes.Key = Sha256(aesKey);
            aes.IV = iv;
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.PKCS7;
            using (var dec = aes.CreateDecryptor())
            {
                return Encoding.UTF8.GetString(dec.TransformFinalBlock(cipher, 0, cipher.Length));
            }
        }
    }

    public static string MakeSign(string data, string appKey)
    {
        using (var md5 = MD5.Create())
        {
            var bytes = md5.ComputeHash(Encoding.UTF8.GetBytes(data + appKey));
            return BitConverter.ToString(bytes).Replace("-", "").ToLowerInvariant();
        }
    }
}