[ubuntu] wifi stops working in secure boot

I am ruing Ubuntu 16.04 on a Dell xps 13 - 9343, which uses a Broadcom wifi. Once I installed the Broadcom driver, the wifi worked fine until the other day when I messed around with some settings, trying to get a live usb recognized in it. I didn't touch it for several days and when I went back to it last night, wifi was not working. When I say not working, I mean it didn't recognize the wifi coection at all in the Network coection manager on the Unity panel; not in Gnome either. I checked Additional Drivers and the Broadcom driver was installed. I confirmed that it was still working in Windows 10. I next coected my Dell to etheet, updated the software and reinstalled the Broadcom driver. Still no recognition of wifi at all. Next, I restarted the Dell and disabled secure boot- the wifi came back. I reconfirmed that the cause was the secure boot setting by restoring secure boot and then removing it. I can certainly live without secure boot, but I'd like to know how this causes a problem with Broadcom wifi, and whether there is a solution that would allow me to enable secure boot and have my wifi back.