那位高人帮我解释一下这个加密和解码代码。我是初学者。。。。

Question

  加密
  public string Encrypt(string pToEncrypt, string key)
        {
            DESCryptoServiceProvider provider = new DESCryptoServiceProvider();            byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);
            provider.Key = ASCIIEncoding.ASCII.GetBytes(key);
            provider.IV = ASCIIEncoding.ASCII.GetBytes(key);
            MemoryStream stream = new MemoryStream();
            CryptoStream crypto = new CryptoStream(stream, provider.CreateEncryptor(), CryptoStreamMode.Write);
            crypto.Write(inputByteArray, 0, inputByteArray.Length);
            crypto.FlushFinalBlock();
            StringBuilder builder = new StringBuilder();
            foreach(byte b in stream.ToArray)
            {
                builder.AppendFormat("{0:X2}", b);
            }
            return builder.ToString();
        }        /******************************************************************
 * 密码解密
 * ******************************************************************/        public string Decrypt(string pToDecrypt, string sKey)
        {
            DESCryptoServiceProvider des = new DESCryptoServiceProvider();
            byte[] inputByteArray = new byte[pToDecrypt.Length / 2];
            for (int x = 0; x < pToDecrypt.Length / 2; x++)
            {
                int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));
                inputByteArray[x] = (byte)i;
            }
            des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
            des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
            MemoryStream ms = new MemoryStream();
            CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
            cs.Write(inputByteArray, 0, inputByteArray.Length);
            cs.FlushFinalBlock();
            StringBuilder ret = new StringBuilder();            return System.Text.Encoding.Default.GetString(ms.ToArray());  
        }非常感谢