Why would my switch be operating with security as ZWAVE_S0_DOWNGRADE instead of S2?
I’d call myself mid-techy but have not looked into S2 and how get that working for these switches.
Thanks in advance!
Kevin
What hub are you using? Very few actually support S2 at this moment (SmartThings doesn’t, Hubitat doesn’t, Home Assistant/Open Z-Wave doesn’t…), so this is pretty common: most (I think all, with rare exceptions) devices that ask for S2 but can’t get it will go for S0 instead.
On the other hand, if you have a reason to think S2 should be working, then I don’t know. 
Smartthings hub V3. Had no idea, just assumed it supported S2. Will keep researching, thanks for replying!
The ST v3 hub is new enough that it should (“must,” technically) support S2, but they got an exemption from the Z-Wave Alliance under the promise that it would be added at some point after its release.
As an update, my latest added switches are communicating with:
networkSecurityLevel: ZWAVE_S2_AUTHENTICATED
@EricM_Inovelli is there an easy way to upgrade all switches that are currently S0 to S2? I do have a z-stick and Z-Wave PC Controller 5.39
The only way to get the device “upgraded” is to exclude it and then include it again with the new SmartThings app. Through the new app you can scan the QR code on the device and get it included with S2.
There is really not much of a benefit of using S2 over S0. S2 mostly fixed a flaw where the network security key is exposed during a “handshake” while including the device. So there is a split second during device inclusion that if someone was sniffing your network they could possibly get your S0 security key. Otherwise the encryption levels are the same between the two security types.
If you are using association between devices they need to be at the same level though. So I could see wanting to upgrade if you are using associations from one Inovelli switch to another.
Interesting, so if my switch is S2 and my ilumin bulb is S0 then association won’t work? Will have to check that out.
Yeah, I believe so. Essentially you have to force the switch to pair in S0 mode by using the classic app or cancelling out of the QR code inclusion process (I think that works). You need the bulb to pair in S0 mode which is easier to do if you pair it as close to the hub as possible.
If I am wrong about an S2 device being able to control an S0 bulb please let me know.
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I’m not an expert, but doesn’t S2 have far less “overhead” than S0, which should result in at least either faster commands/reports or less traffic on your Z-Wave network (making everything better), if not both? I think Hubitat staff have said something like S0 requires three times the back-and-forth compared to “regular” Z-Wave, which S2 reduces significantly. SmartThings obviously may differ (somewhat) in implementation from Hubitat, but Hubitat staff recommend using “regular” Z-Wave everywhere except where needed, e.g., garage doors or locks that require S0, on their hub, so that’s what I’ve been doing. I’d be hesitant to use S0 anywhere given the above if both the hub and device supported S2. (Hubitat does not currently support S2, so S0 is the only option for the above types of secure devices; they have publicly stated that they are experimenting with S2 but don’t have a timeline or official plans for release at the moment.)
But since the Ilumin only supports S0 as far as I can see, I suppose “downgrading” the switch to S0 would be the only option of you want S0/S2 at all on SmartThings and if it’s indeed the case that an S2-paired switch can’t associate with an S0-paired bulb. I might be able to create this setup to test, especially since I have a switch paired to one network with S2 now and just got a couple “unboxed” RGBW bulbs in the mail that I don’t have immediate plans for… 
But anyway, if it were me, I’d use either S2 or nothing unless I can avoid it. (Cough couch, old Schlage lock, cough cough…)
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Feel lucky. I bought the Bluetooth Schlage lock that I can’t even pair with Hubitat…Had I only known that I would be diving into the Smart Home scene…
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Yeah, so you are spot on what you are saying. What I meant by that statement (regarding a benefit of S2 vs S0) was from a security perspective. They both use AES-128 for encryption so other than during inclusion (the weakness I mentioned), their security “level” is the same.
As far as network performance it is true that S0 sends 3x the amount of traffic than non-secure & S2 send. So that can be an impact on network and even controller performance (since the controller has to do some encryption / decryption). A lot of networks are not impacted by this though if the mesh is strong. I have a lot of S0 devices and never have Z-Wave issues. I’ve found that Hubitat is capable of handling the traffic. I have noticed though that Home Assistant sometimes struggles.
As far as my recommendation I merely recommend using S0 in both cases for compatibility with associations since the bulbs only support S0. If association isn’t necessary then definitely go with S2 vs S0. I’m pretty sure you can’t cross security levels S2 to S0 since they are both using different security keys.
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