用户安全加密登录

//用户登录
    protected void btnLogin_Click(object sender, EventArgs e)
    {
        //单击登陆先判断验证码正确后判断用户名和密码；
        string uid = txtUser.Text.Trim().ToString();
        string pwd = txtPwd.Text.Trim().ToString();
        string sql = "select count(*) from 用户注册 where userName= @uid and pwd=@pwd";
        SqlParameter[] paras = new SqlParameter[]{new SqlParameter("@uid", SqlDbType.VarChar, 50),
           new SqlParameter("@pwd", SqlDbType.VarChar, 50)};
        paras[0].Value = uid;
        paras[1].Value = pwd;
        //paras[1].Value =FormsAuthentication.HashPasswordForStoringInConfigFile(pwd, "MD5");                    
        sqlh = new SQLHelper();
        int i = sqlh.ExecuteScalar(sql, paras, CommandType.Text);
        if (i > 0)
        {
            //保存登录信息
            Session["uid"] = uid;
            Session["pwd"] = pwd;
            Response.Redirect("twoPage/selfCenter.aspx");
        }
        else
        {
            Response.Write("<script>alert('密码或用户名错误！')</script>");
        }

    }