C# PageMethods Signing

Default.aspx

<script type="text/javascript" src="js/qz-tray.js"></script>
<script>

qz.security.setSignatureAlgorithm("SHA512"); // Use "SHA1" for QZ Tray 2.0 and older
qz.security.setSignaturePromise(function (toSign) {
    return function (resolve, reject) {
        PageMethods.SignMessage(toSign, resolve, reject);
    };
});
    
qz.security.setCertificatePromise(function (resolve, reject) {
    return $.ajax({ url: "digital-certificate.txt", cache: false, dataType: "text" }).then(resolve, reject);
});

// Unit test
qz.websocket.connect().then(qz.printers.getDefault)
   .then(alert)
   .catch(alert);

</script>

Default.aspx.cs

using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Web.Services;

private static X509KeyStorageFlags STORAGE_FLAGS = X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.Exportable;

[WebMethod]
public static string SignMessage(string request)
{
    //var WEBROOT_PATH = HttpContext.Current.Server.MapPath("/");
    //var CURRENT_PATH = HttpContext.Current.Server.MapPath("~");
    //var PARENT_PATH = System.IO.Directory.GetParent(WEBROOT_PATH).Parent.FullName;
    var KEY = "/path/to/private-key.pfx";
    var PASS = "";

    try
    {
        var cert = new X509Certificate2(KEY, PASS, STORAGE_FLAGS);
        RSACryptoServiceProvider csp = (RSACryptoServiceProvider)cert.PrivateKey;
        byte[] data = new ASCIIEncoding().GetBytes(request);
        byte[] hash = new SHA1CryptoServiceProvider().ComputeHash(data);
        return Convert.ToBase64String(csp.SignHash(hash, CryptoConfig.MapNameToOID("SHA512"))); // Use "SHA1" for QZ Tray 2.0 and older
    }
    catch(Exception ex)
    {
        if((STORAGE_FLAGS & X509KeyStorageFlags.MachineKeySet) == X509KeyStorageFlags.MachineKeySet)
        {
            // IISExpress may fail with "Invalid provider type specified"; remove MachineKeySet flag, try again
            STORAGE_FLAGS = STORAGE_FLAGS & ~X509KeyStorageFlags.MachineKeySet;
            return SignMessage(request);
        }
        throw ex;
    }
}

RouteConfig.cs.diff

- settings.AutoRedirectMode = RedirectMode.Permanent;
+ settings.AutoRedirectMode = RedirectMode.Off;

Site.Master.diff

- <asp:ScriptManager runat="server">
+ <asp:ScriptManager runat="server" EnablePageMethods="true">