How to decrypt the cookie inside custom URL rewrite provider?

FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(
           1,                                    
           model.Email,                          
           DateTime.Now,                          
           DateTime.Now.AddDays(7),          
           true,                         
           "deepak",                             
           FormsAuthentication.FormsCookiePath);  

        string encryptedTicket = FormsAuthentication.Encrypt(ticket);
        HttpCookie fCookie = new HttpCookie("customCookie", encryptedTicket);
        fCookie.Expires = DateTime.Now.AddDays(7);
        fCookie.Path = "/";
        Response.Cookies.Add(fCookie);

public class ParseUserNameProvider : IRewriteProvider, IProviderDescriptor
   {
    public IEnumerable<SettingDescriptor> GetSettings()
    {
        throw new NotImplementedException();
    }

    public void Initialize(IDictionary<string, string> settings, IRewriteContext rewriteContext)
    {}

    public string Rewrite(string value)
    {
        string[] val = value.Split('=');
        string name = "";
        if (val != null)
        {
            FormsAuthenticationTicket authTicket = FormsAuthentication.Decrypt(val[1]);
            if(authTicket!=null)
            {
                name = authTicket.Name;
            }
        }
        return name;
    }
}

Unable to validate data.
      at System.Web.Configuration.MachineKeySection.EncryptOrDecryptData(
      Boolean fEncrypt, Byte[] buf, Byte[] modifier, Int32 start,
      Int32 length, IVType ivType, Boolean useValidationSymAlgo,
      Boolean signData)