I don't totally buy that conclusion. Yes, you won't get any useful security on an Arduino, but there are plenty of small footprint devices that will do full TLS

I don't totally buy that conclusion. Yes, you won't get any useful security on an Arduino, but there are plenty of small footprint devices that will do full TLS. I'm using TI's CC3200 right now with TLS 1.2 using ECDHE_RSA_WITH_AES_256_CBC_SHA to connect to our APIs and this thing is just a Cortex M3 doing all the crypto. (There's probably AES accelerator, but I doubt there is any hardware doing the PKI stuff.) I mean, sure, it's a more expensive chip, it's two ARM cores plus a WiFi MAC in a single package, but it's pretty much all the computing and connectivity you would need for a normal iot kind of application in a less than 1 cm^2.