asp.net – 如何保护存储在web.config中的密码？

<appSettings>
    <add key="ApiURL" value="https://...../servlets/AssetServlet" />
    <add key="ApiUserName" value="tmsservice" />
    <add key="ApiPassword" value="test2test2" />

然后在我的动作方法中,我将在构建Web客户端时引用这些值,如下所示：

public ActionResult Create(RackJoin rj,FormCollection formValues)
        {
XmlDocument doc = new XmlDocument();
using (var client = new WebClient())
                {
                    var query = HttpUtility.ParseQueryString(string.Empty);
                    foreach (string key in formValues)
                    {
                        query[key] = this.Request.Form[key];
                    }

                    query["username"] = System.Web.Configuration.WebConfigurationManager.AppSettings["ApiUserName"];
                    query["password"] = System.Web.Configuration.WebConfigurationManager.AppSettings["ApiPassword"];

                    string apiurl = System.Web.Configuration.WebConfigurationManager.AppSettings["ApiURL"];

但是在这一点上我会暴露用户名和密码,这些可以被用户捕获,所以我的问题是如何保护API用户名和密码？